From 02c2e2ca36101ab650f9444ab9e7fe5b8b00bbf3 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Tue, 5 Apr 2022 18:39:31 +0200 Subject: [PATCH] random: check for signal_pending() outside of need_resched() check commit 1448769c9cdb69ad65287f4f7ab58bc5f2f5d7ba upstream. signal_pending() checks TIF_NOTIFY_SIGNAL and TIF_SIGPENDING, which signal that the task should bail out of the syscall when possible. This is a separate concept from need_resched(), which checks TIF_NEED_RESCHED, signaling that the task should preempt. In particular, with the current code, the signal_pending() bailout probably won't work reliably. Change this to look like other functions that read lots of data, such as read_zero(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jann Horn Signed-off-by: Jason A. Donenfeld Signed-off-by: Greg Kroah-Hartman --- drivers/char/random.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index ab366f5..4ac2131 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -551,13 +551,13 @@ static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) } do { - if (large_request && need_resched()) { + if (large_request) { if (signal_pending(current)) { if (!ret) ret = -ERESTARTSYS; break; } - schedule(); + cond_resched(); } chacha20_block(chacha_state, output); -- 2.7.4