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Subject[PATCH] /dev/zero: fixups for ->read
Date
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>
---
drivers/char/mem.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 1dc99ab158457a..94c2b556cf9728 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -733,14 +733,20 @@ static ssize_t read_zero(struct file *file, char __user *buf,

while (count) {
size_t chunk = min_t(size_t, count, PAGE_SIZE);
+ size_t left;

- if (clear_user(buf + cleared, chunk))
- return cleared ? cleared : -EFAULT;
+ left = clear_user(buf + cleared, chunk);
+ if (unlikely(left)) {
+ cleared += (chunk - left);
+ if (!cleared)
+ return -EFAULT;
+ break;
+ }
cleared += chunk;
count -= chunk;

if (signal_pending(current))
- return cleared ? cleared : -ERESTARTSYS;
+ break;
cond_resched();
}

--
2.28.0
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