diff options
Diffstat (limited to '')
| -rw-r--r-- | include/uapi/linux/bpf.h | 10 | ||||
| -rw-r--r-- | kernel/trace/bpf_trace.c | 45 | ||||
| -rw-r--r-- | samples/bpf/Makefile | 4 | ||||
| -rw-r--r-- | samples/bpf/bpf_helpers.h | 2 | ||||
| -rw-r--r-- | samples/bpf/test_probe_write_user_kern.c | 52 | ||||
| -rw-r--r-- | samples/bpf/test_probe_write_user_user.c | 78 |
6 files changed, 191 insertions, 0 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 2b7076f5b5ad..da218fec6056 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -365,6 +365,16 @@ enum bpf_func_id { */ BPF_FUNC_get_current_task, + /** + * bpf_probe_write_user(void *dst, void *src, int len) + * safely attempt to write to a location + * @dst: destination address in userspace + * @src: source address on stack + * @len: number of bytes to copy + * Return: 0 on success or negative error + */ + BPF_FUNC_probe_write_user, + __BPF_FUNC_MAX_ID, }; diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index a12bbd32c0a6..b20438fdb029 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -81,6 +81,49 @@ static const struct bpf_func_proto bpf_probe_read_proto = { .arg3_type = ARG_ANYTHING, }; +static u64 bpf_probe_write_user(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + void *unsafe_ptr = (void *) (long) r1; + void *src = (void *) (long) r2; + int size = (int) r3; + + /* + * Ensure we're in user context which is safe for the helper to + * run. This helper has no business in a kthread. + * + * access_ok() should prevent writing to non-user memory, but in + * some situations (nommu, temporary switch, etc) access_ok() does + * not provide enough validation, hence the check on KERNEL_DS. + */ + + if (unlikely(in_interrupt() || + current->flags & (PF_KTHREAD | PF_EXITING))) + return -EPERM; + if (unlikely(segment_eq(get_fs(), KERNEL_DS))) + return -EPERM; + if (!access_ok(VERIFY_WRITE, unsafe_ptr, size)) + return -EPERM; + + return probe_kernel_write(unsafe_ptr, src, size); +} + +static const struct bpf_func_proto bpf_probe_write_user_proto = { + .func = bpf_probe_write_user, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_ANYTHING, + .arg2_type = ARG_PTR_TO_STACK, + .arg3_type = ARG_CONST_STACK_SIZE, +}; + +static const struct bpf_func_proto *bpf_get_probe_write_proto(void) +{ + pr_warn_ratelimited("%s[%d] is installing a program with bpf_probe_write_user helper that may corrupt user memory!", + current->comm, task_pid_nr(current)); + + return &bpf_probe_write_user_proto; +} + /* * limited trace_printk() * only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed @@ -362,6 +405,8 @@ static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id) return &bpf_get_smp_processor_id_proto; case BPF_FUNC_perf_event_read: return &bpf_perf_event_read_proto; + case BPF_FUNC_probe_write_user: + return bpf_get_probe_write_proto(); default: return NULL; } diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile index d2d2b35c67eb..90ebf7d35c07 100644 --- a/samples/bpf/Makefile +++ b/samples/bpf/Makefile @@ -14,6 +14,7 @@ hostprogs-y += tracex3 hostprogs-y += tracex4 hostprogs-y += tracex5 hostprogs-y += tracex6 +hostprogs-y += test_probe_write_user hostprogs-y += trace_output hostprogs-y += lathist hostprogs-y += offwaketime @@ -37,6 +38,7 @@ tracex3-objs := bpf_load.o libbpf.o tracex3_user.o tracex4-objs := bpf_load.o libbpf.o tracex4_user.o tracex5-objs := bpf_load.o libbpf.o tracex5_user.o tracex6-objs := bpf_load.o libbpf.o tracex6_user.o +test_probe_write_user-objs := bpf_load.o libbpf.o test_probe_write_user_user.o trace_output-objs := bpf_load.o libbpf.o trace_output_user.o lathist-objs := bpf_load.o libbpf.o lathist_user.o offwaketime-objs := bpf_load.o libbpf.o offwaketime_user.o @@ -59,6 +61,7 @@ always += tracex3_kern.o always += tracex4_kern.o always += tracex5_kern.o always += tracex6_kern.o +always += test_probe_write_user_kern.o always += trace_output_kern.o always += tcbpf1_kern.o always += lathist_kern.o @@ -85,6 +88,7 @@ HOSTLOADLIBES_tracex3 += -lelf HOSTLOADLIBES_tracex4 += -lelf -lrt HOSTLOADLIBES_tracex5 += -lelf HOSTLOADLIBES_tracex6 += -lelf +HOSTLOADLIBES_test_probe_write_user += -lelf HOSTLOADLIBES_trace_output += -lelf -lrt HOSTLOADLIBES_lathist += -lelf HOSTLOADLIBES_offwaketime += -lelf diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h index 84e3fd919a06..217c8d507f2e 100644 --- a/samples/bpf/bpf_helpers.h +++ b/samples/bpf/bpf_helpers.h @@ -41,6 +41,8 @@ static int (*bpf_perf_event_output)(void *ctx, void *map, int index, void *data, (void *) BPF_FUNC_perf_event_output; static int (*bpf_get_stackid)(void *ctx, void *map, int flags) = (void *) BPF_FUNC_get_stackid; +static int (*bpf_probe_write_user)(void *dst, void *src, int size) = + (void *) BPF_FUNC_probe_write_user; /* llvm builtin functions that eBPF C program may use to * emit BPF_LD_ABS and BPF_LD_IND instructions diff --git a/samples/bpf/test_probe_write_user_kern.c b/samples/bpf/test_probe_write_user_kern.c new file mode 100644 index 000000000000..3a677c807044 --- /dev/null +++ b/samples/bpf/test_probe_write_user_kern.c @@ -0,0 +1,52 @@ +/* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + */ +#include <linux/skbuff.h> +#include <linux/netdevice.h> +#include <uapi/linux/bpf.h> +#include <linux/version.h> +#include "bpf_helpers.h" + +struct bpf_map_def SEC("maps") dnat_map = { + .type = BPF_MAP_TYPE_HASH, + .key_size = sizeof(struct sockaddr_in), + .value_size = sizeof(struct sockaddr_in), + .max_entries = 256, +}; + +/* kprobe is NOT a stable ABI + * kernel functions can be removed, renamed or completely change semantics. + * Number of arguments and their positions can change, etc. + * In such case this bpf+kprobe example will no longer be meaningful + * + * This example sits on a syscall, and the syscall ABI is relatively stable + * of course, across platforms, and over time, the ABI may change. + */ +SEC("kprobe/sys_connect") +int bpf_prog1(struct pt_regs *ctx) +{ + struct sockaddr_in new_addr, orig_addr = {}; + struct sockaddr_in *mapped_addr; + void *sockaddr_arg = (void *)PT_REGS_PARM2(ctx); + int sockaddr_len = (int)PT_REGS_PARM3(ctx); + + if (sockaddr_len > sizeof(orig_addr)) + return 0; + + if (bpf_probe_read(&orig_addr, sizeof(orig_addr), sockaddr_arg) != 0) + return 0; + + mapped_addr = bpf_map_lookup_elem(&dnat_map, &orig_addr); + if (mapped_addr != NULL) { + memcpy(&new_addr, mapped_addr, sizeof(new_addr)); + bpf_probe_write_user(sockaddr_arg, &new_addr, + sizeof(new_addr)); + } + return 0; +} + +char _license[] SEC("license") = "GPL"; +u32 _version SEC("version") = LINUX_VERSION_CODE; diff --git a/samples/bpf/test_probe_write_user_user.c b/samples/bpf/test_probe_write_user_user.c new file mode 100644 index 000000000000..a44bf347bedd --- /dev/null +++ b/samples/bpf/test_probe_write_user_user.c @@ -0,0 +1,78 @@ +#include <stdio.h> +#include <assert.h> +#include <linux/bpf.h> +#include <unistd.h> +#include "libbpf.h" +#include "bpf_load.h" +#include <sys/socket.h> +#include <string.h> +#include <netinet/in.h> +#include <arpa/inet.h> + +int main(int ac, char **argv) +{ + int serverfd, serverconnfd, clientfd; + socklen_t sockaddr_len; + struct sockaddr serv_addr, mapped_addr, tmp_addr; + struct sockaddr_in *serv_addr_in, *mapped_addr_in, *tmp_addr_in; + char filename[256]; + char *ip; + + serv_addr_in = (struct sockaddr_in *)&serv_addr; + mapped_addr_in = (struct sockaddr_in *)&mapped_addr; + tmp_addr_in = (struct sockaddr_in *)&tmp_addr; + + snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]); + + if (load_bpf_file(filename)) { + printf("%s", bpf_log_buf); + return 1; + } + + assert((serverfd = socket(AF_INET, SOCK_STREAM, 0)) > 0); + assert((clientfd = socket(AF_INET, SOCK_STREAM, 0)) > 0); + + /* Bind server to ephemeral port on lo */ + memset(&serv_addr, 0, sizeof(serv_addr)); + serv_addr_in->sin_family = AF_INET; + serv_addr_in->sin_port = 0; + serv_addr_in->sin_addr.s_addr = htonl(INADDR_LOOPBACK); + + assert(bind(serverfd, &serv_addr, sizeof(serv_addr)) == 0); + + sockaddr_len = sizeof(serv_addr); + assert(getsockname(serverfd, &serv_addr, &sockaddr_len) == 0); + ip = inet_ntoa(serv_addr_in->sin_addr); + printf("Server bound to: %s:%d\n", ip, ntohs(serv_addr_in->sin_port)); + + memset(&mapped_addr, 0, sizeof(mapped_addr)); + mapped_addr_in->sin_family = AF_INET; + mapped_addr_in->sin_port = htons(5555); + mapped_addr_in->sin_addr.s_addr = inet_addr("255.255.255.255"); + + assert(!bpf_update_elem(map_fd[0], &mapped_addr, &serv_addr, BPF_ANY)); + + assert(listen(serverfd, 5) == 0); + + ip = inet_ntoa(mapped_addr_in->sin_addr); + printf("Client connecting to: %s:%d\n", + ip, ntohs(mapped_addr_in->sin_port)); + assert(connect(clientfd, &mapped_addr, sizeof(mapped_addr)) == 0); + + sockaddr_len = sizeof(tmp_addr); + ip = inet_ntoa(tmp_addr_in->sin_addr); + assert((serverconnfd = accept(serverfd, &tmp_addr, &sockaddr_len)) > 0); + printf("Server received connection from: %s:%d\n", + ip, ntohs(tmp_addr_in->sin_port)); + + sockaddr_len = sizeof(tmp_addr); + assert(getpeername(clientfd, &tmp_addr, &sockaddr_len) == 0); + ip = inet_ntoa(tmp_addr_in->sin_addr); + printf("Client's peer address: %s:%d\n", + ip, ntohs(tmp_addr_in->sin_port)); + + /* Is the server's getsockname = the socket getpeername */ + assert(memcmp(&serv_addr, &tmp_addr, sizeof(struct sockaddr_in)) == 0); + + return 0; +} |