Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 013/264] random: do not ignore early device randomness | Date | Thu, 23 Jun 2022 18:40:06 +0200 |
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From: Kees Cook <keescook@chromium.org>
commit ee7998c50c2697737c6530431709f77c852bf0d6 upstream.
The add_device_randomness() function would ignore incoming bytes if the crng wasn't ready. This additionally makes sure to make an early enough call to add_latent_entropy() to influence the initial stack canary, which is especially important on non-x86 systems where it stays the same through the life of the boot.
Link: http://lkml.kernel.org/r/20170626233038.GA48751@beast Signed-off-by: Kees Cook <keescook@chromium.org> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jessica Yu <jeyu@redhat.com> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: Tejun Heo <tj@kernel.org> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Lokesh Vutla <lokeshvutla@ti.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/char/random.c | 5 +++++ init/main.c | 1 + 2 files changed, 6 insertions(+)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1045,6 +1045,11 @@ void add_device_randomness(const void *b unsigned long time = random_get_entropy() ^ jiffies; unsigned long flags; + if (!crng_ready()) { + crng_fast_load(buf, size); + return; + } + trace_add_device_randomness(size, _RET_IP_); spin_lock_irqsave(&input_pool.lock, flags); _mix_pool_bytes(&input_pool, buf, size); --- a/init/main.c +++ b/init/main.c @@ -490,6 +490,7 @@ asmlinkage __visible void __init start_k /* * Set up the the initial canary ASAP: */ + add_latent_entropy(); boot_init_stack_canary(); cgroup_init_early();
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