Commit 49035eae authored Apr 05, 2022 by Jann Horn Committed by Greg Kroah-Hartman Jun 25, 2022

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: 1da177e4 ("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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 9e790ecb

drivers/char/random.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -549,13 +549,13 @@ 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);