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* [PATCH] zram: off by one in read_block_state()
@ 2021-09-16 13:04 Dan Carpenter
  0 siblings, 0 replies; only message in thread
From: Dan Carpenter @ 2021-09-16 13:04 UTC (permalink / raw)
  To: Minchan Kim
  Cc: Nitin Gupta, Sergey Senozhatsky, Jens Axboe, Andrew Morton,
	linux-kernel, linux-block, kernel-janitors

The snprintf() function 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.

Fixes: c0265342bff4 ("zram: introduce zram memory tracking")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/block/zram/zram_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index fcaf2750f68f..6383c81ac5b3 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -910,7 +910,7 @@ 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;
 		}
-- 
2.20.1


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2021-09-16 13:04 [PATCH] zram: off by one in read_block_state() Dan Carpenter

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