This is a note to let you know that I've just added the patch titled
random: check for signal_pending() outside of need_resched() check
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-check-for-signal_pending-outside-of-need_resched-check.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Jun 17 08:58:56 AM CEST 2022
From: Jann Horn <jannh@xxxxxxxxxx>
Date: Tue, 5 Apr 2022 18:39:31 +0200
Subject: random: check for signal_pending() outside of need_resched() check
From: Jann Horn <jannh@xxxxxxxxxx>
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 <jannh@xxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -549,13 +549,13 @@ static ssize_t get_random_bytes_user(voi
}
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);
Patches currently in stable-queue which might be from jannh@xxxxxxxxxx are
queue-4.19/random-initialize-chacha20-constants-with-correct-endianness.patch
queue-4.19/random-zero-buffer-after-reading-entropy-from-userspace.patch
queue-4.19/random-don-t-reset-crng_init_cnt-on-urandom_read.patch
queue-4.19/random-check-for-signals-every-page_size-chunk-of-dev-random.patch
queue-4.19/random-remove-dead-code-left-over-from-blocking-pool.patch
queue-4.19/random-check-for-signal_pending-outside-of-need_resched-check.patch
queue-4.19/random-remove-outdated-int_max-6-check-in-urandom_read.patch
queue-4.19/random-do-not-allow-user-to-keep-crng-key-around-on-stack.patch
