From: Jann Horn <jannh@google.com>
Date: Tue, 5 Apr 2022 18:39:31 +0200
Subject: random: check for signal_pending() outside of need_resched() check
Git-commit: 1448769c9cdb69ad65287f4f7ab58bc5f2f5d7ba
Patch-mainline: 5.18-rc2
References: git-fixes

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 <jannh@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/char/random.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1035,13 +1035,13 @@ static ssize_t extract_crng_user(void __
 	int large_request = (nbytes > 256);
 
 	while (nbytes) {
-		if (large_request && need_resched()) {
+		if (large_request) {
 			if (signal_pending(current)) {
 				if (ret == 0)
 					ret = -ERESTARTSYS;
 				break;
 			}
-			schedule();
+			cond_resched();
 		}
 
 		extract_crng(tmp);