diff options
Diffstat (limited to 'include/linux/random.h')
-rw-r--r-- | include/linux/random.h | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/random.h b/include/linux/random.h index 4aecc339558d..eafea6a09361 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -58,6 +58,27 @@ static inline unsigned long get_random_long(void) #endif } +/* + * On 64-bit architectures, protect against non-terminated C string overflows + * by zeroing out the first byte of the canary; this leaves 56 bits of entropy. + */ +#ifdef CONFIG_64BIT +# ifdef __LITTLE_ENDIAN +# define CANARY_MASK 0xffffffffffffff00UL +# else /* big endian, 64 bits: */ +# define CANARY_MASK 0x00ffffffffffffffUL +# endif +#else /* 32 bits: */ +# define CANARY_MASK 0xffffffffUL +#endif + +static inline unsigned long get_random_canary(void) +{ + unsigned long val = get_random_long(); + + return val & CANARY_MASK; +} + /* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes). * Returns the result of the call to wait_for_random_bytes. */ static inline int get_random_bytes_wait(void *buf, int nbytes) |