diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/test_printf.c | 108 | ||||
| -rw-r--r-- | lib/vsprintf.c | 194 |
2 files changed, 216 insertions, 86 deletions
diff --git a/lib/test_printf.c b/lib/test_printf.c index 563f10e6876a..71ebfa43ad05 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -24,24 +24,6 @@ #define PAD_SIZE 16 #define FILL_CHAR '$' -#define PTR1 ((void*)0x01234567) -#define PTR2 ((void*)(long)(int)0xfedcba98) - -#if BITS_PER_LONG == 64 -#define PTR1_ZEROES "000000000" -#define PTR1_SPACES " " -#define PTR1_STR "1234567" -#define PTR2_STR "fffffffffedcba98" -#define PTR_WIDTH 16 -#else -#define PTR1_ZEROES "0" -#define PTR1_SPACES " " -#define PTR1_STR "1234567" -#define PTR2_STR "fedcba98" -#define PTR_WIDTH 8 -#endif -#define PTR_WIDTH_STR stringify(PTR_WIDTH) - static unsigned total_tests __initdata; static unsigned failed_tests __initdata; static char *test_buffer __initdata; @@ -217,30 +199,79 @@ test_string(void) test("a | | ", "%-3.s|%-3.0s|%-3.*s", "a", "b", 0, "c"); } +#define PLAIN_BUF_SIZE 64 /* leave some space so we don't oops */ + +#if BITS_PER_LONG == 64 + +#define PTR_WIDTH 16 +#define PTR ((void *)0xffff0123456789ab) +#define PTR_STR "ffff0123456789ab" +#define ZEROS "00000000" /* hex 32 zero bits */ + +static int __init +plain_format(void) +{ + char buf[PLAIN_BUF_SIZE]; + int nchars; + + nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR); + + if (nchars != PTR_WIDTH || strncmp(buf, ZEROS, strlen(ZEROS)) != 0) + return -1; + + return 0; +} + +#else + +#define PTR_WIDTH 8 +#define PTR ((void *)0x456789ab) +#define PTR_STR "456789ab" + +static int __init +plain_format(void) +{ + /* Format is implicitly tested for 32 bit machines by plain_hash() */ + return 0; +} + +#endif /* BITS_PER_LONG == 64 */ + +static int __init +plain_hash(void) +{ + char buf[PLAIN_BUF_SIZE]; + int nchars; + + nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR); + + if (nchars != PTR_WIDTH || strncmp(buf, PTR_STR, PTR_WIDTH) == 0) + return -1; + + return 0; +} + +/* + * We can't use test() to test %p because we don't know what output to expect + * after an address is hashed. + */ static void __init plain(void) { - test(PTR1_ZEROES PTR1_STR " " PTR2_STR, "%p %p", PTR1, PTR2); - /* - * The field width is overloaded for some %p extensions to - * pass another piece of information. For plain pointers, the - * behaviour is slightly odd: One cannot pass either the 0 - * flag nor a precision to %p without gcc complaining, and if - * one explicitly gives a field width, the number is no longer - * zero-padded. - */ - test("|" PTR1_STR PTR1_SPACES " | " PTR1_SPACES PTR1_STR "|", - "|%-*p|%*p|", PTR_WIDTH+2, PTR1, PTR_WIDTH+2, PTR1); - test("|" PTR2_STR " | " PTR2_STR "|", - "|%-*p|%*p|", PTR_WIDTH+2, PTR2, PTR_WIDTH+2, PTR2); + int err; - /* - * Unrecognized %p extensions are treated as plain %p, but the - * alphanumeric suffix is ignored (that is, does not occur in - * the output.) - */ - test("|"PTR1_ZEROES PTR1_STR"|", "|%p0y|", PTR1); - test("|"PTR2_STR"|", "|%p0y|", PTR2); + err = plain_hash(); + if (err) { + pr_warn("plain 'p' does not appear to be hashed\n"); + failed_tests++; + return; + } + + err = plain_format(); + if (err) { + pr_warn("hashing plain 'p' has unexpected format\n"); + failed_tests++; + } } static void __init @@ -251,6 +282,7 @@ symbol_ptr(void) static void __init kernel_ptr(void) { + /* We can't test this without access to kptr_restrict. */ } static void __init diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 1746bae94d41..01c3957b2de6 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -33,6 +33,8 @@ #include <linux/uuid.h> #include <linux/of.h> #include <net/addrconf.h> +#include <linux/siphash.h> +#include <linux/compiler.h> #ifdef CONFIG_BLOCK #include <linux/blkdev.h> #endif @@ -1343,6 +1345,59 @@ char *uuid_string(char *buf, char *end, const u8 *addr, return string(buf, end, uuid, spec); } +int kptr_restrict __read_mostly; + +static noinline_for_stack +char *restricted_pointer(char *buf, char *end, const void *ptr, + struct printf_spec spec) +{ + spec.base = 16; + spec.flags |= SMALL; + if (spec.field_width == -1) { + spec.field_width = 2 * sizeof(ptr); + spec.flags |= ZEROPAD; + } + + switch (kptr_restrict) { + case 0: + /* Always print %pK values */ + break; + case 1: { + const struct cred *cred; + + /* + * kptr_restrict==1 cannot be used in IRQ context + * because its test for CAP_SYSLOG would be meaningless. + */ + if (in_irq() || in_serving_softirq() || in_nmi()) + return string(buf, end, "pK-error", spec); + + /* + * Only print the real pointer value if the current + * process has CAP_SYSLOG and is running with the + * same credentials it started with. This is because + * access to files is checked at open() time, but %pK + * checks permission at read() time. We don't want to + * leak pointer values if a binary opens a file using + * %pK and then elevates privileges before reading it. + */ + cred = current_cred(); + if (!has_capability_noaudit(current, CAP_SYSLOG) || + !uid_eq(cred->euid, cred->uid) || + !gid_eq(cred->egid, cred->gid)) + ptr = NULL; + break; + } + case 2: + default: + /* Always print 0's for %pK */ + ptr = NULL; + break; + } + + return number(buf, end, (unsigned long)ptr, spec); +} + static noinline_for_stack char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt) { @@ -1591,7 +1646,86 @@ char *device_node_string(char *buf, char *end, struct device_node *dn, return widen_string(buf, buf - buf_start, end, spec); } -int kptr_restrict __read_mostly; +static noinline_for_stack +char *pointer_string(char *buf, char *end, const void *ptr, + struct printf_spec spec) +{ + spec.base = 16; + spec.flags |= SMALL; + if (spec.field_width == -1) { + spec.field_width = 2 * sizeof(ptr); + spec.flags |= ZEROPAD; + } + + return number(buf, end, (unsigned long int)ptr, spec); +} + +static bool have_filled_random_ptr_key __read_mostly; +static siphash_key_t ptr_key __read_mostly; + +static void fill_random_ptr_key(struct random_ready_callback *unused) +{ + get_random_bytes(&ptr_key, sizeof(ptr_key)); + /* + * have_filled_random_ptr_key==true is dependent on get_random_bytes(). + * ptr_to_id() needs to see have_filled_random_ptr_key==true + * after get_random_bytes() returns. + */ + smp_mb(); + WRITE_ONCE(have_filled_random_ptr_key, true); +} + +static struct random_ready_callback random_ready = { + .func = fill_random_ptr_key +}; + +static int __init initialize_ptr_random(void) +{ + int ret = add_random_ready_callback(&random_ready); + + if (!ret) { + return 0; + } else if (ret == -EALREADY) { + fill_random_ptr_key(&random_ready); + return 0; + } + + return ret; +} +early_initcall(initialize_ptr_random); + +/* Maps a pointer to a 32 bit unique identifier. */ +static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec spec) +{ + unsigned long hashval; + const int default_width = 2 * sizeof(ptr); + + if (unlikely(!have_filled_random_ptr_key)) { + spec.field_width = default_width; + /* string length must be less than default_width */ + return string(buf, end, "(ptrval)", spec); + } + +#ifdef CONFIG_64BIT + hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key); + /* + * Mask off the first 32 bits, this makes explicit that we have + * modified the address (and 32 bits is plenty for a unique ID). + */ + hashval = hashval & 0xffffffff; +#else + hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key); +#endif + + spec.flags |= SMALL; + if (spec.field_width == -1) { + spec.field_width = default_width; + spec.flags |= ZEROPAD; + } + spec.base = 16; + + return number(buf, end, hashval, spec); +} /* * Show a '%p' thing. A kernel extension is that the '%p' is followed @@ -1698,11 +1832,16 @@ int kptr_restrict __read_mostly; * c major compatible string * C full compatible string * + * - 'x' For printing the address. Equivalent to "%lx". + * * ** Please update also Documentation/printk-formats.txt when making changes ** * * Note: The difference between 'S' and 'F' is that on ia64 and ppc64 * function pointers are really function descriptors, which contain a * pointer to the real address. + * + * Note: The default behaviour (unadorned %p) is to hash the address, + * rendering it useful as a unique identifier. */ static noinline_for_stack char *pointer(const char *fmt, char *buf, char *end, void *ptr, @@ -1792,47 +1931,9 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, return buf; } case 'K': - switch (kptr_restrict) { - case 0: - /* Always print %pK values */ - break; - case 1: { - const struct cred *cred; - - /* - * kptr_restrict==1 cannot be used in IRQ context - * because its test for CAP_SYSLOG would be meaningless. - */ - if (in_irq() || in_serving_softirq() || in_nmi()) { - if (spec.field_width == -1) - spec.field_width = default_width; - return string(buf, end, "pK-error", spec); - } - - /* - * Only print the real pointer value if the current - * process has CAP_SYSLOG and is running with the - * same credentials it started with. This is because - * access to files is checked at open() time, but %pK - * checks permission at read() time. We don't want to - * leak pointer values if a binary opens a file using - * %pK and then elevates privileges before reading it. - */ - cred = current_cred(); - if (!has_capability_noaudit(current, CAP_SYSLOG) || - !uid_eq(cred->euid, cred->uid) || - !gid_eq(cred->egid, cred->gid)) - ptr = NULL; - break; - } - case 2: - default: - /* Always print 0's for %pK */ - ptr = NULL; + if (!kptr_restrict) break; - } - break; - + return restricted_pointer(buf, end, ptr, spec); case 'N': return netdev_bits(buf, end, ptr, fmt); case 'a': @@ -1857,15 +1958,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, case 'F': return device_node_string(buf, end, ptr, spec, fmt + 1); } + case 'x': + return pointer_string(buf, end, ptr, spec); } - spec.flags |= SMALL; - if (spec.field_width == -1) { - spec.field_width = default_width; - spec.flags |= ZEROPAD; - } - spec.base = 16; - return number(buf, end, (unsigned long) ptr, spec); + /* default is to _not_ leak addresses, hash before printing */ + return ptr_to_id(buf, end, ptr, spec); } /* |