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zram: off by one in read_block_state()

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[ Upstream commit a88e03cf3d ]

snprintf() returns the number of bytes it would have printed if there
were space.  But it does not count the NUL terminator.  So that means
that if "count == copied" then this has already overflowed by one
character.

This bug likely isn't super harmful in real life.

Link: https://lkml.kernel.org/r/20210916130404.GA25094@kili
Fixes: c0265342bf ("zram: introduce zram memory tracking")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dan Carpenter 2021-11-05 13:45:12 -07:00 • committed by Greg Kroah-Hartman
commit 7091fcc75f
1 changed files with 1 additions and 1 deletions
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drivers/block/zram/zram_drv.c
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@ -907,7 +907,7 @@ static ssize_t read_block_state(struct file *file, char __user *buf,
zram_test_flag(zram, index, ZRAM_HUGE) ? 'h' : '.',
zram_test_flag(zram, index, ZRAM_IDLE) ? 'i' : '.');
if (count < copied) {
if (count <= copied) {
zram_slot_unlock(zram, index);
break;
}