[PATCH 4.9 58/91] bcache: fix input overflow to cache set sysfs file io_error_halflife

[Greg Kroah-Hartman]

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

------------------

[ Upstream commit a91fbda49f746119828f7e8ad0f0aa2ab0578f65 ]

Cache set sysfs entry io_error_halflife is used to set c->error_decay.
c->error_decay is in type unsigned int, and it is converted by
strtoul_or_return(), therefore overflow to c->error_decay is possible
for a large input value.

This patch fixes the overflow by using strtoul_safe_clamp() to convert
input string to an unsigned long value in range [0, UINT_MAX], then
divides by 88 and set it to c->error_decay.

Signed-off-by: Coly Li <colyli@xxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/md/bcache/sysfs.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 5a5c1f1bd8a5..87daccbbc61b 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -645,8 +645,17 @@ STORE(__bch_cache_set)
 		c->error_limit = strtoul_or_return(buf) << IO_ERROR_SHIFT;
 
 	/* See count_io_errors() for why 88 */
-	if (attr == &sysfs_io_error_halflife)
-		c->error_decay = strtoul_or_return(buf) / 88;
+	if (attr == &sysfs_io_error_halflife) {
+		unsigned long v = 0;
+		ssize_t ret;
+
+		ret = strtoul_safe_clamp(buf, v, 0, UINT_MAX);
+		if (!ret) {
+			c->error_decay = v / 88;
+			return size;
+		}
+		return ret;
+	}
 
 	sysfs_strtoul(journal_delay_ms,		c->journal_delay_ms);
 	sysfs_strtoul(verify,			c->verify);
-- 
2.19.1