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/dev/zero: fixups for ->read 

Reported the cleared bytes in case of a partial clear_user instead
of -EFAULT, and remove a pointless conditional, as cleared must be
non-zero by the time we hit the signal_pending check.

Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20200907082700.2057137-1-hch@lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christoph Hellwig 2020-09-07 10:27:00 +02:00 committed by Greg Kroah-Hartman
parent 947bece14b
commit ab04de8ec2
1 changed files with 9 additions and 3 deletions
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12
drivers/char/mem.c
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@ -733,14 +733,20 @@ static ssize_t read_zero(struct file *file, char __user *buf,
while (count) { while (count) {
size_t chunk = min_t(size_t, count, PAGE_SIZE); size_t chunk = min_t(size_t, count, PAGE_SIZE);
size_t left;
if (clear_user(buf + cleared, chunk)) left = clear_user(buf + cleared, chunk);
return cleared ? cleared : -EFAULT; if (unlikely(left)) {
cleared += (chunk - left);
if (!cleared)
return -EFAULT;
break;
}
cleared += chunk; cleared += chunk;
count -= chunk; count -= chunk;
if (signal_pending(current)) if (signal_pending(current))
return cleared ? cleared : -ERESTARTSYS; break;
cond_resched(); cond_resched();
} }