From 2ec9898e9c70b93a5741af3f6af6dbceca569a47 Mon Sep 17 00:00:00 2001
From: He Fengqing <hefengqing@huawei.com>
Date: Wed, 31 Mar 2021 07:51:35 +0000
Subject: bpf: Remove unused parameter from ___bpf_prog_run

'stack' parameter is not used in ___bpf_prog_run() after f696b8f471ec
("bpf: split bpf core interpreter"), the base address have been set to
FP reg. So consequently remove it.

Signed-off-by: He Fengqing <hefengqing@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210331075135.3850782-1-hefengqing@huawei.com
---
 kernel/bpf/core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

(limited to 'kernel')

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f5423251c118..5e31ee9f7512 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1363,11 +1363,10 @@ u64 __weak bpf_probe_read_kernel(void *dst, u32 size, const void *unsafe_ptr)
  *	__bpf_prog_run - run eBPF program on a given context
  *	@regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers
  *	@insn: is the array of eBPF instructions
- *	@stack: is the eBPF storage stack
  *
  * Decode and execute eBPF instructions.
  */
-static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
+static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 {
 #define BPF_INSN_2_LBL(x, y)    [BPF_##x | BPF_##y] = &&x##_##y
 #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = &&x##_##y##_##z
@@ -1701,7 +1700,7 @@ static unsigned int PROG_NAME(stack_size)(const void *ctx, const struct bpf_insn
 \
 	FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)]; \
 	ARG1 = (u64) (unsigned long) ctx; \
-	return ___bpf_prog_run(regs, insn, stack); \
+	return ___bpf_prog_run(regs, insn); \
 }
 
 #define PROG_NAME_ARGS(stack_size) __bpf_prog_run_args##stack_size
@@ -1718,7 +1717,7 @@ static u64 PROG_NAME_ARGS(stack_size)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5, \
 	BPF_R3 = r3; \
 	BPF_R4 = r4; \
 	BPF_R5 = r5; \
-	return ___bpf_prog_run(regs, insn, stack); \
+	return ___bpf_prog_run(regs, insn); \
 }
 
 #define EVAL1(FN, X) FN(X)
-- 
cgit v1.2.3-59-g8ed1b


From 957dca3df624abcbf895f5081fc664693aa0b363 Mon Sep 17 00:00:00 2001
From: Muhammad Usama Anjum <musamaanjum@gmail.com>
Date: Tue, 6 Apr 2021 00:49:04 +0500
Subject: bpf, inode: Remove second initialization of the bpf_preload_lock

bpf_preload_lock is already defined with DEFINE_MUTEX(). There is no
need to initialize it again. Remove the extraneous initialization.

Signed-off-by: Muhammad Usama Anjum <musamaanjum@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210405194904.GA148013@LEGION
---
 kernel/bpf/inode.c | 2 --
 1 file changed, 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 1576ff331ee4..f441d521ef77 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -816,8 +816,6 @@ static int __init bpf_init(void)
 {
 	int ret;
 
-	mutex_init(&bpf_preload_lock);
-
 	ret = sysfs_create_mount_point(fs_kobj, "bpf");
 	if (ret)
 		return ret;
-- 
cgit v1.2.3-59-g8ed1b


From 441e8c66b23e027c00ccebd70df9fd933918eefe Mon Sep 17 00:00:00 2001
From: Toke Høiland-Jørgensen <toke@redhat.com>
Date: Tue, 13 Apr 2021 11:16:06 +0200
Subject: bpf: Return target info when a tracing bpf_link is queried
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

There is currently no way to discover the target of a tracing program
attachment after the fact. Add this information to bpf_link_info and return
it when querying the bpf_link fd.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210413091607.58945-1-toke@redhat.com
---
 include/linux/bpf_verifier.h   | 9 +++++++++
 include/uapi/linux/bpf.h       | 2 ++
 kernel/bpf/syscall.c           | 3 +++
 tools/include/uapi/linux/bpf.h | 2 ++
 4 files changed, 16 insertions(+)

(limited to 'kernel')

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 51c2ffa3d901..6023a1367853 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -487,6 +487,15 @@ static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
 		return ((u64)btf_obj_id(btf) << 32) | 0x80000000 | btf_id;
 }
 
+/* unpack the IDs from the key as constructed above */
+static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id)
+{
+	if (obj_id)
+		*obj_id = key >> 32;
+	if (btf_id)
+		*btf_id = key & 0x7FFFFFFF;
+}
+
 int bpf_check_attach_target(struct bpf_verifier_log *log,
 			    const struct bpf_prog *prog,
 			    const struct bpf_prog *tgt_prog,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 85c924bc21b1..df164a44bb41 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5416,6 +5416,8 @@ struct bpf_link_info {
 		} raw_tracepoint;
 		struct {
 			__u32 attach_type;
+			__u32 target_obj_id; /* prog_id for PROG_EXT, otherwise btf object id */
+			__u32 target_btf_id; /* BTF type id inside the object */
 		} tracing;
 		struct {
 			__u64 cgroup_id;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6428634da57e..fd495190115e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2551,6 +2551,9 @@ static int bpf_tracing_link_fill_link_info(const struct bpf_link *link,
 		container_of(link, struct bpf_tracing_link, link);
 
 	info->tracing.attach_type = tr_link->attach_type;
+	bpf_trampoline_unpack_key(tr_link->trampoline->key,
+				  &info->tracing.target_obj_id,
+				  &info->tracing.target_btf_id);
 
 	return 0;
 }
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 85c924bc21b1..df164a44bb41 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5416,6 +5416,8 @@ struct bpf_link_info {
 		} raw_tracepoint;
 		struct {
 			__u32 attach_type;
+			__u32 target_obj_id; /* prog_id for PROG_EXT, otherwise btf object id */
+			__u32 target_btf_id; /* BTF type id inside the object */
 		} tracing;
 		struct {
 			__u64 cgroup_id;
-- 
cgit v1.2.3-59-g8ed1b


From d9c9e4db186ab4d81f84e6f22b225d333b9424e3 Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@chromium.org>
Date: Mon, 19 Apr 2021 17:52:38 +0200
Subject: bpf: Factorize bpf_trace_printk and bpf_seq_printf

Two helpers (trace_printk and seq_printf) have very similar
implementations of format string parsing and a third one is coming
(snprintf). To avoid code duplication and make the code easier to
maintain, this moves the operations associated with format string
parsing (validation and argument sanitization) into one generic
function.

The implementation of the two existing helpers already drifted quite a
bit so unifying them entailed a lot of changes:

- bpf_trace_printk always expected fmt[fmt_size] to be the terminating
  NULL character, this is no longer true, the first 0 is terminating.
- bpf_trace_printk now supports %% (which produces the percentage char).
- bpf_trace_printk now skips width formating fields.
- bpf_trace_printk now supports the X modifier (capital hexadecimal).
- bpf_trace_printk now supports %pK, %px, %pB, %pi4, %pI4, %pi6 and %pI6
- argument casting on 32 bit has been simplified into one macro and
  using an enum instead of obscure int increments.

- bpf_seq_printf now uses bpf_trace_copy_string instead of
  strncpy_from_kernel_nofault and handles the %pks %pus specifiers.
- bpf_seq_printf now prints longs correctly on 32 bit architectures.

- both were changed to use a global per-cpu tmp buffer instead of one
  stack buffer for trace_printk and 6 small buffers for seq_printf.
- to avoid per-cpu buffer usage conflict, these helpers disable
  preemption while the per-cpu buffer is in use.
- both helpers now support the %ps and %pS specifiers to print symbols.

The implementation is also moved from bpf_trace.c to helpers.c because
the upcoming bpf_snprintf helper will be made available to all BPF
programs and will need it.

Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210419155243.1632274-2-revest@chromium.org
---
 include/linux/bpf.h      |  20 +++
 kernel/bpf/helpers.c     | 256 ++++++++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c | 371 +++++------------------------------------------
 3 files changed, 313 insertions(+), 334 deletions(-)

(limited to 'kernel')

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ff8cd68c01b3..77d1d8c65b81 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2077,4 +2077,24 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 struct btf_id_set;
 bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
 
+enum bpf_printf_mod_type {
+	BPF_PRINTF_INT,
+	BPF_PRINTF_LONG,
+	BPF_PRINTF_LONG_LONG,
+};
+
+/* Workaround for getting va_list handling working with different argument type
+ * combinations generically for 32 and 64 bit archs.
+ */
+#define BPF_CAST_FMT_ARG(arg_nb, args, mod)				\
+	(mod[arg_nb] == BPF_PRINTF_LONG_LONG ||				\
+	 (mod[arg_nb] == BPF_PRINTF_LONG && __BITS_PER_LONG == 64)	\
+	  ? (u64)args[arg_nb]						\
+	  : (u32)args[arg_nb])
+
+int bpf_printf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
+		       u64 *final_args, enum bpf_printf_mod_type *mod,
+		       u32 num_args);
+void bpf_printf_cleanup(void);
+
 #endif /* _LINUX_BPF_H */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index f306611c4ddf..9ca57eb1fc0d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -669,6 +669,262 @@ const struct bpf_func_proto bpf_this_cpu_ptr_proto = {
 	.arg1_type	= ARG_PTR_TO_PERCPU_BTF_ID,
 };
 
+static int bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype,
+		size_t bufsz)
+{
+	void __user *user_ptr = (__force void __user *)unsafe_ptr;
+
+	buf[0] = 0;
+
+	switch (fmt_ptype) {
+	case 's':
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+		if ((unsigned long)unsafe_ptr < TASK_SIZE)
+			return strncpy_from_user_nofault(buf, user_ptr, bufsz);
+		fallthrough;
+#endif
+	case 'k':
+		return strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
+	case 'u':
+		return strncpy_from_user_nofault(buf, user_ptr, bufsz);
+	}
+
+	return -EINVAL;
+}
+
+/* Per-cpu temp buffers which can be used by printf-like helpers for %s or %p
+ */
+#define MAX_PRINTF_BUF_LEN	512
+
+struct bpf_printf_buf {
+	char tmp_buf[MAX_PRINTF_BUF_LEN];
+};
+static DEFINE_PER_CPU(struct bpf_printf_buf, bpf_printf_buf);
+static DEFINE_PER_CPU(int, bpf_printf_buf_used);
+
+static int try_get_fmt_tmp_buf(char **tmp_buf)
+{
+	struct bpf_printf_buf *bufs;
+	int used;
+
+	if (*tmp_buf)
+		return 0;
+
+	preempt_disable();
+	used = this_cpu_inc_return(bpf_printf_buf_used);
+	if (WARN_ON_ONCE(used > 1)) {
+		this_cpu_dec(bpf_printf_buf_used);
+		preempt_enable();
+		return -EBUSY;
+	}
+	bufs = this_cpu_ptr(&bpf_printf_buf);
+	*tmp_buf = bufs->tmp_buf;
+
+	return 0;
+}
+
+void bpf_printf_cleanup(void)
+{
+	if (this_cpu_read(bpf_printf_buf_used)) {
+		this_cpu_dec(bpf_printf_buf_used);
+		preempt_enable();
+	}
+}
+
+/*
+ * bpf_parse_fmt_str - Generic pass on format strings for printf-like helpers
+ *
+ * Returns a negative value if fmt is an invalid format string or 0 otherwise.
+ *
+ * This can be used in two ways:
+ * - Format string verification only: when final_args and mod are NULL
+ * - Arguments preparation: in addition to the above verification, it writes in
+ *   final_args a copy of raw_args where pointers from BPF have been sanitized
+ *   into pointers safe to use by snprintf. This also writes in the mod array
+ *   the size requirement of each argument, usable by BPF_CAST_FMT_ARG for ex.
+ *
+ * In argument preparation mode, if 0 is returned, safe temporary buffers are
+ * allocated and bpf_printf_cleanup should be called to free them after use.
+ */
+int bpf_printf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
+			u64 *final_args, enum bpf_printf_mod_type *mod,
+			u32 num_args)
+{
+	char *unsafe_ptr = NULL, *tmp_buf = NULL, *fmt_end;
+	size_t tmp_buf_len = MAX_PRINTF_BUF_LEN;
+	int err, i, num_spec = 0, copy_size;
+	enum bpf_printf_mod_type cur_mod;
+	u64 cur_arg;
+	char fmt_ptype;
+
+	if (!!final_args != !!mod)
+		return -EINVAL;
+
+	fmt_end = strnchr(fmt, fmt_size, 0);
+	if (!fmt_end)
+		return -EINVAL;
+	fmt_size = fmt_end - fmt;
+
+	for (i = 0; i < fmt_size; i++) {
+		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) {
+			err = -EINVAL;
+			goto cleanup;
+		}
+
+		if (fmt[i] != '%')
+			continue;
+
+		if (fmt[i + 1] == '%') {
+			i++;
+			continue;
+		}
+
+		if (num_spec >= num_args) {
+			err = -EINVAL;
+			goto cleanup;
+		}
+
+		/* The string is zero-terminated so if fmt[i] != 0, we can
+		 * always access fmt[i + 1], in the worst case it will be a 0
+		 */
+		i++;
+
+		/* skip optional "[0 +-][num]" width formatting field */
+		while (fmt[i] == '0' || fmt[i] == '+'  || fmt[i] == '-' ||
+		       fmt[i] == ' ')
+			i++;
+		if (fmt[i] >= '1' && fmt[i] <= '9') {
+			i++;
+			while (fmt[i] >= '0' && fmt[i] <= '9')
+				i++;
+		}
+
+		if (fmt[i] == 'p') {
+			cur_mod = BPF_PRINTF_LONG;
+
+			if ((fmt[i + 1] == 'k' || fmt[i + 1] == 'u') &&
+			    fmt[i + 2] == 's') {
+				fmt_ptype = fmt[i + 1];
+				i += 2;
+				goto fmt_str;
+			}
+
+			if (fmt[i + 1] == 0 || isspace(fmt[i + 1]) ||
+			    ispunct(fmt[i + 1]) || fmt[i + 1] == 'K' ||
+			    fmt[i + 1] == 'x' || fmt[i + 1] == 'B' ||
+			    fmt[i + 1] == 's' || fmt[i + 1] == 'S') {
+				/* just kernel pointers */
+				if (final_args)
+					cur_arg = raw_args[num_spec];
+				goto fmt_next;
+			}
+
+			/* only support "%pI4", "%pi4", "%pI6" and "%pi6". */
+			if ((fmt[i + 1] != 'i' && fmt[i + 1] != 'I') ||
+			    (fmt[i + 2] != '4' && fmt[i + 2] != '6')) {
+				err = -EINVAL;
+				goto cleanup;
+			}
+
+			i += 2;
+			if (!final_args)
+				goto fmt_next;
+
+			if (try_get_fmt_tmp_buf(&tmp_buf)) {
+				err = -EBUSY;
+				goto out;
+			}
+
+			copy_size = (fmt[i + 2] == '4') ? 4 : 16;
+			if (tmp_buf_len < copy_size) {
+				err = -ENOSPC;
+				goto cleanup;
+			}
+
+			unsafe_ptr = (char *)(long)raw_args[num_spec];
+			err = copy_from_kernel_nofault(tmp_buf, unsafe_ptr,
+						       copy_size);
+			if (err < 0)
+				memset(tmp_buf, 0, copy_size);
+			cur_arg = (u64)(long)tmp_buf;
+			tmp_buf += copy_size;
+			tmp_buf_len -= copy_size;
+
+			goto fmt_next;
+		} else if (fmt[i] == 's') {
+			cur_mod = BPF_PRINTF_LONG;
+			fmt_ptype = fmt[i];
+fmt_str:
+			if (fmt[i + 1] != 0 &&
+			    !isspace(fmt[i + 1]) &&
+			    !ispunct(fmt[i + 1])) {
+				err = -EINVAL;
+				goto cleanup;
+			}
+
+			if (!final_args)
+				goto fmt_next;
+
+			if (try_get_fmt_tmp_buf(&tmp_buf)) {
+				err = -EBUSY;
+				goto out;
+			}
+
+			if (!tmp_buf_len) {
+				err = -ENOSPC;
+				goto cleanup;
+			}
+
+			unsafe_ptr = (char *)(long)raw_args[num_spec];
+			err = bpf_trace_copy_string(tmp_buf, unsafe_ptr,
+						    fmt_ptype, tmp_buf_len);
+			if (err < 0) {
+				tmp_buf[0] = '\0';
+				err = 1;
+			}
+
+			cur_arg = (u64)(long)tmp_buf;
+			tmp_buf += err;
+			tmp_buf_len -= err;
+
+			goto fmt_next;
+		}
+
+		cur_mod = BPF_PRINTF_INT;
+
+		if (fmt[i] == 'l') {
+			cur_mod = BPF_PRINTF_LONG;
+			i++;
+		}
+		if (fmt[i] == 'l') {
+			cur_mod = BPF_PRINTF_LONG_LONG;
+			i++;
+		}
+
+		if (fmt[i] != 'i' && fmt[i] != 'd' && fmt[i] != 'u' &&
+		    fmt[i] != 'x' && fmt[i] != 'X') {
+			err = -EINVAL;
+			goto cleanup;
+		}
+
+		if (final_args)
+			cur_arg = raw_args[num_spec];
+fmt_next:
+		if (final_args) {
+			mod[num_spec] = cur_mod;
+			final_args[num_spec] = cur_arg;
+		}
+		num_spec++;
+	}
+
+	err = 0;
+cleanup:
+	if (err)
+		bpf_printf_cleanup();
+out:
+	return err;
+}
+
 const struct bpf_func_proto bpf_get_current_task_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0d23755c2747..a13f8644b357 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -372,188 +372,38 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
 	return &bpf_probe_write_user_proto;
 }
 
-static void bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype,
-		size_t bufsz)
-{
-	void __user *user_ptr = (__force void __user *)unsafe_ptr;
-
-	buf[0] = 0;
-
-	switch (fmt_ptype) {
-	case 's':
-#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
-		if ((unsigned long)unsafe_ptr < TASK_SIZE) {
-			strncpy_from_user_nofault(buf, user_ptr, bufsz);
-			break;
-		}
-		fallthrough;
-#endif
-	case 'k':
-		strncpy_from_kernel_nofault(buf, unsafe_ptr, bufsz);
-		break;
-	case 'u':
-		strncpy_from_user_nofault(buf, user_ptr, bufsz);
-		break;
-	}
-}
-
 static DEFINE_RAW_SPINLOCK(trace_printk_lock);
 
-#define BPF_TRACE_PRINTK_SIZE   1024
+#define MAX_TRACE_PRINTK_VARARGS	3
+#define BPF_TRACE_PRINTK_SIZE		1024
 
-static __printf(1, 0) int bpf_do_trace_printk(const char *fmt, ...)
+BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
+	   u64, arg2, u64, arg3)
 {
+	u64 args[MAX_TRACE_PRINTK_VARARGS] = { arg1, arg2, arg3 };
+	enum bpf_printf_mod_type mod[MAX_TRACE_PRINTK_VARARGS];
 	static char buf[BPF_TRACE_PRINTK_SIZE];
 	unsigned long flags;
-	va_list ap;
 	int ret;
 
-	raw_spin_lock_irqsave(&trace_printk_lock, flags);
-	va_start(ap, fmt);
-	ret = vsnprintf(buf, sizeof(buf), fmt, ap);
-	va_end(ap);
-	/* vsnprintf() will not append null for zero-length strings */
+	ret = bpf_printf_prepare(fmt, fmt_size, args, args, mod,
+				 MAX_TRACE_PRINTK_VARARGS);
+	if (ret < 0)
+		return ret;
+
+	ret = snprintf(buf, sizeof(buf), fmt, BPF_CAST_FMT_ARG(0, args, mod),
+		BPF_CAST_FMT_ARG(1, args, mod), BPF_CAST_FMT_ARG(2, args, mod));
+	/* snprintf() will not append null for zero-length strings */
 	if (ret == 0)
 		buf[0] = '\0';
+
+	raw_spin_lock_irqsave(&trace_printk_lock, flags);
 	trace_bpf_trace_printk(buf);
 	raw_spin_unlock_irqrestore(&trace_printk_lock, flags);
 
-	return ret;
-}
-
-/*
- * Only limited trace_printk() conversion specifiers allowed:
- * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pB %pks %pus %s
- */
-BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
-	   u64, arg2, u64, arg3)
-{
-	int i, mod[3] = {}, fmt_cnt = 0;
-	char buf[64], fmt_ptype;
-	void *unsafe_ptr = NULL;
-	bool str_seen = false;
+	bpf_printf_cleanup();
 
-	/*
-	 * bpf_check()->check_func_arg()->check_stack_boundary()
-	 * guarantees that fmt points to bpf program stack,
-	 * fmt_size bytes of it were initialized and fmt_size > 0
-	 */
-	if (fmt[--fmt_size] != 0)
-		return -EINVAL;
-
-	/* check format string for allowed specifiers */
-	for (i = 0; i < fmt_size; i++) {
-		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
-			return -EINVAL;
-
-		if (fmt[i] != '%')
-			continue;
-
-		if (fmt_cnt >= 3)
-			return -EINVAL;
-
-		/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
-		i++;
-		if (fmt[i] == 'l') {
-			mod[fmt_cnt]++;
-			i++;
-		} else if (fmt[i] == 'p') {
-			mod[fmt_cnt]++;
-			if ((fmt[i + 1] == 'k' ||
-			     fmt[i + 1] == 'u') &&
-			    fmt[i + 2] == 's') {
-				fmt_ptype = fmt[i + 1];
-				i += 2;
-				goto fmt_str;
-			}
-
-			if (fmt[i + 1] == 'B') {
-				i++;
-				goto fmt_next;
-			}
-
-			/* disallow any further format extensions */
-			if (fmt[i + 1] != 0 &&
-			    !isspace(fmt[i + 1]) &&
-			    !ispunct(fmt[i + 1]))
-				return -EINVAL;
-
-			goto fmt_next;
-		} else if (fmt[i] == 's') {
-			mod[fmt_cnt]++;
-			fmt_ptype = fmt[i];
-fmt_str:
-			if (str_seen)
-				/* allow only one '%s' per fmt string */
-				return -EINVAL;
-			str_seen = true;
-
-			if (fmt[i + 1] != 0 &&
-			    !isspace(fmt[i + 1]) &&
-			    !ispunct(fmt[i + 1]))
-				return -EINVAL;
-
-			switch (fmt_cnt) {
-			case 0:
-				unsafe_ptr = (void *)(long)arg1;
-				arg1 = (long)buf;
-				break;
-			case 1:
-				unsafe_ptr = (void *)(long)arg2;
-				arg2 = (long)buf;
-				break;
-			case 2:
-				unsafe_ptr = (void *)(long)arg3;
-				arg3 = (long)buf;
-				break;
-			}
-
-			bpf_trace_copy_string(buf, unsafe_ptr, fmt_ptype,
-					sizeof(buf));
-			goto fmt_next;
-		}
-
-		if (fmt[i] == 'l') {
-			mod[fmt_cnt]++;
-			i++;
-		}
-
-		if (fmt[i] != 'i' && fmt[i] != 'd' &&
-		    fmt[i] != 'u' && fmt[i] != 'x')
-			return -EINVAL;
-fmt_next:
-		fmt_cnt++;
-	}
-
-/* Horrid workaround for getting va_list handling working with different
- * argument type combinations generically for 32 and 64 bit archs.
- */
-#define __BPF_TP_EMIT()	__BPF_ARG3_TP()
-#define __BPF_TP(...)							\
-	bpf_do_trace_printk(fmt, ##__VA_ARGS__)
-
-#define __BPF_ARG1_TP(...)						\
-	((mod[0] == 2 || (mod[0] == 1 && __BITS_PER_LONG == 64))	\
-	  ? __BPF_TP(arg1, ##__VA_ARGS__)				\
-	  : ((mod[0] == 1 || (mod[0] == 0 && __BITS_PER_LONG == 32))	\
-	      ? __BPF_TP((long)arg1, ##__VA_ARGS__)			\
-	      : __BPF_TP((u32)arg1, ##__VA_ARGS__)))
-
-#define __BPF_ARG2_TP(...)						\
-	((mod[1] == 2 || (mod[1] == 1 && __BITS_PER_LONG == 64))	\
-	  ? __BPF_ARG1_TP(arg2, ##__VA_ARGS__)				\
-	  : ((mod[1] == 1 || (mod[1] == 0 && __BITS_PER_LONG == 32))	\
-	      ? __BPF_ARG1_TP((long)arg2, ##__VA_ARGS__)		\
-	      : __BPF_ARG1_TP((u32)arg2, ##__VA_ARGS__)))
-
-#define __BPF_ARG3_TP(...)						\
-	((mod[2] == 2 || (mod[2] == 1 && __BITS_PER_LONG == 64))	\
-	  ? __BPF_ARG2_TP(arg3, ##__VA_ARGS__)				\
-	  : ((mod[2] == 1 || (mod[2] == 0 && __BITS_PER_LONG == 32))	\
-	      ? __BPF_ARG2_TP((long)arg3, ##__VA_ARGS__)		\
-	      : __BPF_ARG2_TP((u32)arg3, ##__VA_ARGS__)))
-
-	return __BPF_TP_EMIT();
+	return ret;
 }
 
 static const struct bpf_func_proto bpf_trace_printk_proto = {
@@ -581,184 +431,37 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
 }
 
 #define MAX_SEQ_PRINTF_VARARGS		12
-#define MAX_SEQ_PRINTF_MAX_MEMCPY	6
-#define MAX_SEQ_PRINTF_STR_LEN		128
-
-struct bpf_seq_printf_buf {
-	char buf[MAX_SEQ_PRINTF_MAX_MEMCPY][MAX_SEQ_PRINTF_STR_LEN];
-};
-static DEFINE_PER_CPU(struct bpf_seq_printf_buf, bpf_seq_printf_buf);
-static DEFINE_PER_CPU(int, bpf_seq_printf_buf_used);
 
 BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
 	   const void *, data, u32, data_len)
 {
-	int err = -EINVAL, fmt_cnt = 0, memcpy_cnt = 0;
-	int i, buf_used, copy_size, num_args;
-	u64 params[MAX_SEQ_PRINTF_VARARGS];
-	struct bpf_seq_printf_buf *bufs;
-	const u64 *args = data;
-
-	buf_used = this_cpu_inc_return(bpf_seq_printf_buf_used);
-	if (WARN_ON_ONCE(buf_used > 1)) {
-		err = -EBUSY;
-		goto out;
-	}
-
-	bufs = this_cpu_ptr(&bpf_seq_printf_buf);
-
-	/*
-	 * bpf_check()->check_func_arg()->check_stack_boundary()
-	 * guarantees that fmt points to bpf program stack,
-	 * fmt_size bytes of it were initialized and fmt_size > 0
-	 */
-	if (fmt[--fmt_size] != 0)
-		goto out;
-
-	if (data_len & 7)
-		goto out;
-
-	for (i = 0; i < fmt_size; i++) {
-		if (fmt[i] == '%') {
-			if (fmt[i + 1] == '%')
-				i++;
-			else if (!data || !data_len)
-				goto out;
-		}
-	}
+	enum bpf_printf_mod_type mod[MAX_SEQ_PRINTF_VARARGS];
+	u64 args[MAX_SEQ_PRINTF_VARARGS];
+	int err, num_args;
 
+	if (data_len & 7 || data_len > MAX_SEQ_PRINTF_VARARGS * 8 ||
+	    (data_len && !data))
+		return -EINVAL;
 	num_args = data_len / 8;
 
-	/* check format string for allowed specifiers */
-	for (i = 0; i < fmt_size; i++) {
-		/* only printable ascii for now. */
-		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) {
-			err = -EINVAL;
-			goto out;
-		}
-
-		if (fmt[i] != '%')
-			continue;
-
-		if (fmt[i + 1] == '%') {
-			i++;
-			continue;
-		}
-
-		if (fmt_cnt >= MAX_SEQ_PRINTF_VARARGS) {
-			err = -E2BIG;
-			goto out;
-		}
-
-		if (fmt_cnt >= num_args) {
-			err = -EINVAL;
-			goto out;
-		}
-
-		/* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
-		i++;
-
-		/* skip optional "[0 +-][num]" width formating field */
-		while (fmt[i] == '0' || fmt[i] == '+'  || fmt[i] == '-' ||
-		       fmt[i] == ' ')
-			i++;
-		if (fmt[i] >= '1' && fmt[i] <= '9') {
-			i++;
-			while (fmt[i] >= '0' && fmt[i] <= '9')
-				i++;
-		}
-
-		if (fmt[i] == 's') {
-			void *unsafe_ptr;
-
-			/* try our best to copy */
-			if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
-				err = -E2BIG;
-				goto out;
-			}
-
-			unsafe_ptr = (void *)(long)args[fmt_cnt];
-			err = strncpy_from_kernel_nofault(bufs->buf[memcpy_cnt],
-					unsafe_ptr, MAX_SEQ_PRINTF_STR_LEN);
-			if (err < 0)
-				bufs->buf[memcpy_cnt][0] = '\0';
-			params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];
-
-			fmt_cnt++;
-			memcpy_cnt++;
-			continue;
-		}
-
-		if (fmt[i] == 'p') {
-			if (fmt[i + 1] == 0 ||
-			    fmt[i + 1] == 'K' ||
-			    fmt[i + 1] == 'x' ||
-			    fmt[i + 1] == 'B') {
-				/* just kernel pointers */
-				params[fmt_cnt] = args[fmt_cnt];
-				fmt_cnt++;
-				continue;
-			}
-
-			/* only support "%pI4", "%pi4", "%pI6" and "%pi6". */
-			if (fmt[i + 1] != 'i' && fmt[i + 1] != 'I') {
-				err = -EINVAL;
-				goto out;
-			}
-			if (fmt[i + 2] != '4' && fmt[i + 2] != '6') {
-				err = -EINVAL;
-				goto out;
-			}
-
-			if (memcpy_cnt >= MAX_SEQ_PRINTF_MAX_MEMCPY) {
-				err = -E2BIG;
-				goto out;
-			}
-
-
-			copy_size = (fmt[i + 2] == '4') ? 4 : 16;
-
-			err = copy_from_kernel_nofault(bufs->buf[memcpy_cnt],
-						(void *) (long) args[fmt_cnt],
-						copy_size);
-			if (err < 0)
-				memset(bufs->buf[memcpy_cnt], 0, copy_size);
-			params[fmt_cnt] = (u64)(long)bufs->buf[memcpy_cnt];
-
-			i += 2;
-			fmt_cnt++;
-			memcpy_cnt++;
-			continue;
-		}
-
-		if (fmt[i] == 'l') {
-			i++;
-			if (fmt[i] == 'l')
-				i++;
-		}
-
-		if (fmt[i] != 'i' && fmt[i] != 'd' &&
-		    fmt[i] != 'u' && fmt[i] != 'x' &&
-		    fmt[i] != 'X') {
-			err = -EINVAL;
-			goto out;
-		}
-
-		params[fmt_cnt] = args[fmt_cnt];
-		fmt_cnt++;
-	}
+	err = bpf_printf_prepare(fmt, fmt_size, data, args, mod, num_args);
+	if (err < 0)
+		return err;
 
 	/* Maximumly we can have MAX_SEQ_PRINTF_VARARGS parameter, just give
 	 * all of them to seq_printf().
 	 */
-	seq_printf(m, fmt, params[0], params[1], params[2], params[3],
-		   params[4], params[5], params[6], params[7], params[8],
-		   params[9], params[10], params[11]);
+	seq_printf(m, fmt, BPF_CAST_FMT_ARG(0, args, mod),
+		BPF_CAST_FMT_ARG(1, args, mod), BPF_CAST_FMT_ARG(2, args, mod),
+		BPF_CAST_FMT_ARG(3, args, mod), BPF_CAST_FMT_ARG(4, args, mod),
+		BPF_CAST_FMT_ARG(5, args, mod), BPF_CAST_FMT_ARG(6, args, mod),
+		BPF_CAST_FMT_ARG(7, args, mod), BPF_CAST_FMT_ARG(8, args, mod),
+		BPF_CAST_FMT_ARG(9, args, mod), BPF_CAST_FMT_ARG(10, args, mod),
+		BPF_CAST_FMT_ARG(11, args, mod));
 
-	err = seq_has_overflowed(m) ? -EOVERFLOW : 0;
-out:
-	this_cpu_dec(bpf_seq_printf_buf_used);
-	return err;
+	bpf_printf_cleanup();
+
+	return seq_has_overflowed(m) ? -EOVERFLOW : 0;
 }
 
 BTF_ID_LIST_SINGLE(btf_seq_file_ids, struct, seq_file)
-- 
cgit v1.2.3-59-g8ed1b


From fff13c4bb646ef849fd74ced87eef54340d28c21 Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@chromium.org>
Date: Mon, 19 Apr 2021 17:52:39 +0200
Subject: bpf: Add a ARG_PTR_TO_CONST_STR argument type

This type provides the guarantee that an argument is going to be a const
pointer to somewhere in a read-only map value. It also checks that this
pointer is followed by a zero character before the end of the map value.

Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210419155243.1632274-3-revest@chromium.org
---
 include/linux/bpf.h   |  1 +
 kernel/bpf/verifier.c | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

(limited to 'kernel')

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 77d1d8c65b81..c160526fc8bf 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -309,6 +309,7 @@ enum bpf_arg_type {
 	ARG_PTR_TO_PERCPU_BTF_ID,	/* pointer to in-kernel percpu type */
 	ARG_PTR_TO_FUNC,	/* pointer to a bpf program function */
 	ARG_PTR_TO_STACK_OR_NULL,	/* pointer to stack or NULL */
+	ARG_PTR_TO_CONST_STR,	/* pointer to a null terminated read-only string */
 	__BPF_ARG_TYPE_MAX,
 };
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 852541a435ef..5f46dd6f3383 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4787,6 +4787,7 @@ static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALU
 static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_PERCPU_BTF_ID } };
 static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
 static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };
+static const struct bpf_reg_types const_str_ptr_types = { .types = { PTR_TO_MAP_VALUE } };
 
 static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_MAP_KEY]		= &map_key_value_types,
@@ -4817,6 +4818,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_PERCPU_BTF_ID]	= &percpu_btf_ptr_types,
 	[ARG_PTR_TO_FUNC]		= &func_ptr_types,
 	[ARG_PTR_TO_STACK_OR_NULL]	= &stack_ptr_types,
+	[ARG_PTR_TO_CONST_STR]		= &const_str_ptr_types,
 };
 
 static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
@@ -5067,6 +5069,45 @@ skip_type_check:
 		if (err)
 			return err;
 		err = check_ptr_alignment(env, reg, 0, size, true);
+	} else if (arg_type == ARG_PTR_TO_CONST_STR) {
+		struct bpf_map *map = reg->map_ptr;
+		int map_off;
+		u64 map_addr;
+		char *str_ptr;
+
+		if (reg->type != PTR_TO_MAP_VALUE || !map ||
+		    !bpf_map_is_rdonly(map)) {
+			verbose(env, "R%d does not point to a readonly map'\n", regno);
+			return -EACCES;
+		}
+
+		if (!tnum_is_const(reg->var_off)) {
+			verbose(env, "R%d is not a constant address'\n", regno);
+			return -EACCES;
+		}
+
+		if (!map->ops->map_direct_value_addr) {
+			verbose(env, "no direct value access support for this map type\n");
+			return -EACCES;
+		}
+
+		err = check_map_access(env, regno, reg->off,
+				       map->value_size - reg->off, false);
+		if (err)
+			return err;
+
+		map_off = reg->off + reg->var_off.value;
+		err = map->ops->map_direct_value_addr(map, &map_addr, map_off);
+		if (err) {
+			verbose(env, "direct value access on string failed\n");
+			return err;
+		}
+
+		str_ptr = (char *)(long)(map_addr);
+		if (!strnchr(str_ptr + map_off, map->value_size - map_off, 0)) {
+			verbose(env, "string is not zero-terminated\n");
+			return -EINVAL;
+		}
 	}
 
 	return err;
-- 
cgit v1.2.3-59-g8ed1b


From 7b15523a989b63927c2bb08e9b5b0bbc10b58bef Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@chromium.org>
Date: Mon, 19 Apr 2021 17:52:40 +0200
Subject: bpf: Add a bpf_snprintf helper

The implementation takes inspiration from the existing bpf_trace_printk
helper but there are a few differences:

To allow for a large number of format-specifiers, parameters are
provided in an array, like in bpf_seq_printf.

Because the output string takes two arguments and the array of
parameters also takes two arguments, the format string needs to fit in
one argument. Thankfully, ARG_PTR_TO_CONST_STR is guaranteed to point to
a zero-terminated read-only map so we don't need a format string length
arg.

Because the format-string is known at verification time, we also do
a first pass of format string validation in the verifier logic. This
makes debugging easier.

Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210419155243.1632274-4-revest@chromium.org
---
 include/linux/bpf.h            |  1 +
 include/uapi/linux/bpf.h       | 28 +++++++++++++++++++++++
 kernel/bpf/helpers.c           | 50 ++++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c          | 41 ++++++++++++++++++++++++++++++++++
 kernel/trace/bpf_trace.c       |  2 ++
 tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++++++
 6 files changed, 150 insertions(+)

(limited to 'kernel')

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c160526fc8bf..f8a45f109e96 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1953,6 +1953,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
 extern const struct bpf_func_proto bpf_copy_from_user_proto;
 extern const struct bpf_func_proto bpf_snprintf_btf_proto;
+extern const struct bpf_func_proto bpf_snprintf_proto;
 extern const struct bpf_func_proto bpf_per_cpu_ptr_proto;
 extern const struct bpf_func_proto bpf_this_cpu_ptr_proto;
 extern const struct bpf_func_proto bpf_ktime_get_coarse_ns_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index df164a44bb41..ec6d85a81744 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4708,6 +4708,33 @@ union bpf_attr {
  *	Return
  *		The number of traversed map elements for success, **-EINVAL** for
  *		invalid **flags**.
+ *
+ * long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 *data, u32 data_len)
+ *	Description
+ *		Outputs a string into the **str** buffer of size **str_size**
+ *		based on a format string stored in a read-only map pointed by
+ *		**fmt**.
+ *
+ *		Each format specifier in **fmt** corresponds to one u64 element
+ *		in the **data** array. For strings and pointers where pointees
+ *		are accessed, only the pointer values are stored in the *data*
+ *		array. The *data_len* is the size of *data* in bytes.
+ *
+ *		Formats **%s** and **%p{i,I}{4,6}** require to read kernel
+ *		memory. Reading kernel memory may fail due to either invalid
+ *		address or valid address but requiring a major memory fault. If
+ *		reading kernel memory fails, the string for **%s** will be an
+ *		empty string, and the ip address for **%p{i,I}{4,6}** will be 0.
+ *		Not returning error to bpf program is consistent with what
+ *		**bpf_trace_printk**\ () does for now.
+ *
+ *	Return
+ *		The strictly positive length of the formatted string, including
+ *		the trailing zero character. If the return value is greater than
+ *		**str_size**, **str** contains a truncated string, guaranteed to
+ *		be zero-terminated except when **str_size** is 0.
+ *
+ *		Or **-EBUSY** if the per-CPU memory copy buffer is busy.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4875,6 +4902,7 @@ union bpf_attr {
 	FN(sock_from_file),		\
 	FN(check_mtu),			\
 	FN(for_each_map_elem),		\
+	FN(snprintf),			\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 9ca57eb1fc0d..85b26ca5aacd 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -925,6 +925,54 @@ out:
 	return err;
 }
 
+#define MAX_SNPRINTF_VARARGS		12
+
+BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
+	   const void *, data, u32, data_len)
+{
+	enum bpf_printf_mod_type mod[MAX_SNPRINTF_VARARGS];
+	u64 args[MAX_SNPRINTF_VARARGS];
+	int err, num_args;
+
+	if (data_len % 8 || data_len > MAX_SNPRINTF_VARARGS * 8 ||
+	    (data_len && !data))
+		return -EINVAL;
+	num_args = data_len / 8;
+
+	/* ARG_PTR_TO_CONST_STR guarantees that fmt is zero-terminated so we
+	 * can safely give an unbounded size.
+	 */
+	err = bpf_printf_prepare(fmt, UINT_MAX, data, args, mod, num_args);
+	if (err < 0)
+		return err;
+
+	/* Maximumly we can have MAX_SNPRINTF_VARARGS parameters, just give
+	 * all of them to snprintf().
+	 */
+	err = snprintf(str, str_size, fmt, BPF_CAST_FMT_ARG(0, args, mod),
+		BPF_CAST_FMT_ARG(1, args, mod), BPF_CAST_FMT_ARG(2, args, mod),
+		BPF_CAST_FMT_ARG(3, args, mod), BPF_CAST_FMT_ARG(4, args, mod),
+		BPF_CAST_FMT_ARG(5, args, mod), BPF_CAST_FMT_ARG(6, args, mod),
+		BPF_CAST_FMT_ARG(7, args, mod), BPF_CAST_FMT_ARG(8, args, mod),
+		BPF_CAST_FMT_ARG(9, args, mod), BPF_CAST_FMT_ARG(10, args, mod),
+		BPF_CAST_FMT_ARG(11, args, mod));
+
+	bpf_printf_cleanup();
+
+	return err + 1;
+}
+
+const struct bpf_func_proto bpf_snprintf_proto = {
+	.func		= bpf_snprintf,
+	.gpl_only	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_MEM_OR_NULL,
+	.arg2_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg3_type	= ARG_PTR_TO_CONST_STR,
+	.arg4_type	= ARG_PTR_TO_MEM_OR_NULL,
+	.arg5_type	= ARG_CONST_SIZE_OR_ZERO,
+};
+
 const struct bpf_func_proto bpf_get_current_task_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
@@ -1013,6 +1061,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_probe_read_kernel_str_proto;
 	case BPF_FUNC_snprintf_btf:
 		return &bpf_snprintf_btf_proto;
+	case BPF_FUNC_snprintf:
+		return &bpf_snprintf_proto;
 	default:
 		return NULL;
 	}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5f46dd6f3383..994ef36c5f60 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5918,6 +5918,41 @@ static int check_reference_leak(struct bpf_verifier_env *env)
 	return state->acquired_refs ? -EINVAL : 0;
 }
 
+static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
+				   struct bpf_reg_state *regs)
+{
+	struct bpf_reg_state *fmt_reg = &regs[BPF_REG_3];
+	struct bpf_reg_state *data_len_reg = &regs[BPF_REG_5];
+	struct bpf_map *fmt_map = fmt_reg->map_ptr;
+	int err, fmt_map_off, num_args;
+	u64 fmt_addr;
+	char *fmt;
+
+	/* data must be an array of u64 */
+	if (data_len_reg->var_off.value % 8)
+		return -EINVAL;
+	num_args = data_len_reg->var_off.value / 8;
+
+	/* fmt being ARG_PTR_TO_CONST_STR guarantees that var_off is const
+	 * and map_direct_value_addr is set.
+	 */
+	fmt_map_off = fmt_reg->off + fmt_reg->var_off.value;
+	err = fmt_map->ops->map_direct_value_addr(fmt_map, &fmt_addr,
+						  fmt_map_off);
+	if (err)
+		return err;
+	fmt = (char *)(long)fmt_addr + fmt_map_off;
+
+	/* We are also guaranteed that fmt+fmt_map_off is NULL terminated, we
+	 * can focus on validating the format specifiers.
+	 */
+	err = bpf_printf_prepare(fmt, UINT_MAX, NULL, NULL, NULL, num_args);
+	if (err < 0)
+		verbose(env, "Invalid format string\n");
+
+	return err;
+}
+
 static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			     int *insn_idx_p)
 {
@@ -6032,6 +6067,12 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 			return -EINVAL;
 	}
 
+	if (func_id == BPF_FUNC_snprintf) {
+		err = check_bpf_snprintf_call(env, regs);
+		if (err < 0)
+			return err;
+	}
+
 	/* reset caller saved regs */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		mark_reg_not_init(env, regs, caller_saved[i]);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a13f8644b357..2a8bcdc927c7 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1076,6 +1076,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_task_storage_delete_proto;
 	case BPF_FUNC_for_each_map_elem:
 		return &bpf_for_each_map_elem_proto;
+	case BPF_FUNC_snprintf:
+		return &bpf_snprintf_proto;
 	default:
 		return NULL;
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index df164a44bb41..ec6d85a81744 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4708,6 +4708,33 @@ union bpf_attr {
  *	Return
  *		The number of traversed map elements for success, **-EINVAL** for
  *		invalid **flags**.
+ *
+ * long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 *data, u32 data_len)
+ *	Description
+ *		Outputs a string into the **str** buffer of size **str_size**
+ *		based on a format string stored in a read-only map pointed by
+ *		**fmt**.
+ *
+ *		Each format specifier in **fmt** corresponds to one u64 element
+ *		in the **data** array. For strings and pointers where pointees
+ *		are accessed, only the pointer values are stored in the *data*
+ *		array. The *data_len* is the size of *data* in bytes.
+ *
+ *		Formats **%s** and **%p{i,I}{4,6}** require to read kernel
+ *		memory. Reading kernel memory may fail due to either invalid
+ *		address or valid address but requiring a major memory fault. If
+ *		reading kernel memory fails, the string for **%s** will be an
+ *		empty string, and the ip address for **%p{i,I}{4,6}** will be 0.
+ *		Not returning error to bpf program is consistent with what
+ *		**bpf_trace_printk**\ () does for now.
+ *
+ *	Return
+ *		The strictly positive length of the formatted string, including
+ *		the trailing zero character. If the return value is greater than
+ *		**str_size**, **str** contains a truncated string, guaranteed to
+ *		be zero-terminated except when **str_size** is 0.
+ *
+ *		Or **-EBUSY** if the per-CPU memory copy buffer is busy.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -4875,6 +4902,7 @@ union bpf_attr {
 	FN(sock_from_file),		\
 	FN(check_mtu),			\
 	FN(for_each_map_elem),		\
+	FN(snprintf),			\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
cgit v1.2.3-59-g8ed1b


From fd0b88f73f5372c08ceff5cc7ddd8ceac502679c Mon Sep 17 00:00:00 2001
From: Dave Marchevsky <davemarchevsky@fb.com>
Date: Fri, 16 Apr 2021 13:47:02 -0700
Subject: bpf: Refine retval for bpf_get_task_stack helper

Verifier can constrain the min/max bounds of bpf_get_task_stack's return
value more tightly than the default tnum_unknown. Like bpf_get_stack,
return value is num bytes written into a caller-supplied buf, or error,
so do_refine_retval_range will work.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210416204704.2816874-2-davemarchevsky@fb.com
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'kernel')

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 994ef36c5f60..58730872f7e5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5808,6 +5808,7 @@ static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
 
 	if (ret_type != RET_INTEGER ||
 	    (func_id != BPF_FUNC_get_stack &&
+	     func_id != BPF_FUNC_get_task_stack &&
 	     func_id != BPF_FUNC_probe_read_str &&
 	     func_id != BPF_FUNC_probe_read_kernel_str &&
 	     func_id != BPF_FUNC_probe_read_user_str))
-- 
cgit v1.2.3-59-g8ed1b


From 8e8ee109b02c0e90021d63cd20dd0157c021f7a4 Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@chromium.org>
Date: Fri, 23 Apr 2021 01:55:42 +0200
Subject: bpf: Notify user if we ever hit a bpf_snprintf verifier bug

In check_bpf_snprintf_call(), a map_direct_value_addr() of the fmt map
should never fail because it has already been checked by
ARG_PTR_TO_CONST_STR. But if it ever fails, it's better to error out
with an explicit debug message rather than silently fail.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210422235543.4007694-2-revest@chromium.org
---
 kernel/bpf/verifier.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 58730872f7e5..59799a9b014a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5940,8 +5940,10 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
 	fmt_map_off = fmt_reg->off + fmt_reg->var_off.value;
 	err = fmt_map->ops->map_direct_value_addr(fmt_map, &fmt_addr,
 						  fmt_map_off);
-	if (err)
-		return err;
+	if (err) {
+		verbose(env, "verifier bug\n");
+		return -EFAULT;
+	}
 	fmt = (char *)(long)fmt_addr + fmt_map_off;
 
 	/* We are also guaranteed that fmt+fmt_map_off is NULL terminated, we
-- 
cgit v1.2.3-59-g8ed1b


From a8fad73e3334151196acb28c4dcde37732c82542 Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@chromium.org>
Date: Fri, 23 Apr 2021 01:55:43 +0200
Subject: bpf: Remove unnecessary map checks for ARG_PTR_TO_CONST_STR

reg->type is enforced by check_reg_type() and map should never be NULL
(it would already have been dereferenced anyway) so these checks are
unnecessary.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210422235543.4007694-3-revest@chromium.org
---
 kernel/bpf/verifier.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 59799a9b014a..2579f6fbb5c3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5075,8 +5075,7 @@ skip_type_check:
 		u64 map_addr;
 		char *str_ptr;
 
-		if (reg->type != PTR_TO_MAP_VALUE || !map ||
-		    !bpf_map_is_rdonly(map)) {
+		if (!bpf_map_is_rdonly(map)) {
 			verbose(env, "R%d does not point to a readonly map'\n", regno);
 			return -EACCES;
 		}
-- 
cgit v1.2.3-59-g8ed1b