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random: check for signal_pending() outside of need_resched() check 

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: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jann Horn 2022-04-05 18:39:31 +02:00 committed by Jason A. Donenfeld
parent aba120cc10
commit 1448769c9c
1 changed files with 2 additions and 2 deletions
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4
drivers/char/random.c
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@ -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);