[PATCH 3.12 071/123] dm stats: fix divide by zero if 'number_of_areas' arg is zero

[Jiri Slaby]

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit dd4c1b7d0c95be1c9245118a3accc41a16f1db67 upstream.

If the number_of_areas argument was zero the kernel would crash on
div-by-zero.  Add better input validation.

Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/md/dm-stats.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 28a90122a5a8..b3b0697a9fd7 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -795,6 +795,8 @@ static int message_stats_create(struct mapped_device *md,
 		return -EINVAL;
 
 	if (sscanf(argv[2], "/%u%c", &divisor, &dummy) == 1) {
+		if (!divisor)
+			return -EINVAL;
 		step = end - start;
 		if (do_div(step, divisor))
 			step++;
-- 
2.5.0

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