Messages in this thread Patch in this message | | | From | Prarit Bhargava <> | Subject | [PATCH] x86, random: Fix get_random_bytes() warning in x86 start_kernel | Date | Tue, 29 May 2018 08:38:00 -0400 |
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After 43838a23a05f ("random: fix crng_ready() test") early boot calls to get_random_bytes() will warn on each cpu on x86 because the crng is not initialized. For example,
random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0
x86 only uses get_random_bytes() for better randomization of the stack canary value so the warning is of no consequence.
Export crng_ready() for x86 and test if the crng is initialized before calling get_random_bytes().
Signed-off-by: Prarit Bhargava <prarit@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Kees Cook <keescook@chromium.org> Cc: Prarit Bhargava <prarit@redhat.com> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Cc: Kate Stewart <kstewart@linuxfoundation.org> --- arch/x86/include/asm/stackprotector.h | 3 ++- drivers/char/random.c | 5 ++++- include/linux/random.h | 1 + 3 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 371b3a4af000..4e2223aa34fc 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -72,7 +72,8 @@ static __always_inline void boot_init_stack_canary(void) * there it already has some randomness on most systems. Later * on during the bootup the random pool has true entropy too. */ - get_random_bytes(&canary, sizeof(canary)); + if (crng_ready()) + get_random_bytes(&canary, sizeof(canary)); tsc = rdtsc(); canary += tsc + (tsc << 32UL); canary &= CANARY_MASK; diff --git a/drivers/char/random.c b/drivers/char/random.c index cd888d4ee605..003091d104bf 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -428,7 +428,10 @@ struct crng_state primary_crng = { * its value (from 0->1->2). */ static int crng_init = 0; -#define crng_ready() (likely(crng_init > 1)) +int crng_ready(void) +{ + return likely(crng_init > 1); +} static int crng_init_cnt = 0; static unsigned long crng_global_init_time = 0; #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE) diff --git a/include/linux/random.h b/include/linux/random.h index 2ddf13b4281e..45616513abd9 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -196,4 +196,5 @@ static inline u32 next_pseudo_random32(u32 seed) return seed * 1664525 + 1013904223; } +extern int crng_ready(void); #endif /* _LINUX_RANDOM_H */ -- 2.14.3
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