From: "Jason A. Donenfeld" Jason@zx2c4.com
stable inclusion from stable-v5.10.119 commit 083ab33951e45a4e7521241ee9e1570139bf66f0 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6BB
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 3e504d2026eb6c8762cd6040ae57db166516824a upstream.
Rather than waiting a full second in an interruptable waiter before trying to generate entropy, try to generate entropy first and wait second. While waiting one second might give an extra second for getting entropy from elsewhere, we're already pretty late in the init process here, and whatever else is generating entropy will still continue to contribute. This has implications on signal handling: we call try_to_generate_entropy() from wait_for_random_bytes(), and wait_for_random_bytes() always uses wait_event_interruptible_timeout() when waiting, since it's called by userspace code in restartable contexts, where signals can pend. Since try_to_generate_entropy() now runs first, if a signal is pending, it's necessary for try_to_generate_entropy() to check for signals, since it won't hit the wait until after try_to_generate_entropy() has returned. And even before this change, when entering a busy loop in try_to_generate_entropy(), we should have been checking to see if any signals are pending, so that a process doesn't get stuck in that loop longer than expected.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Acked-by: Xie XiuQi xiexiuqi@huawei.com --- drivers/char/random.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c index 4187cc8e4cb7..4c0a12c9052b 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -127,10 +127,11 @@ int wait_for_random_bytes(void) { while (!crng_ready()) { int ret; + + try_to_generate_entropy(); ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ); if (ret) return ret > 0 ? 0 : ret; - try_to_generate_entropy(); } return 0; } @@ -1371,7 +1372,7 @@ static void try_to_generate_entropy(void) return;
timer_setup_on_stack(&stack.timer, entropy_timer, 0); - while (!crng_ready()) { + while (!crng_ready() && !signal_pending(current)) { if (!timer_pending(&stack.timer)) mod_timer(&stack.timer, jiffies + 1); mix_pool_bytes(&stack.cycles, sizeof(stack.cycles));