for-next/sysfs-fix/0011-bcache-fix-input-overflow-to-cache-set-sysfs-file-io.patch

From 9a9512d0e4913257d3eeb31a1e096ef090371300 Mon Sep 17 00:00:00 2001
From: Coly Li <colyli@suse.de>
Date: Thu, 20 Dec 2018 22:31:25 +0800
Subject: [PATCH 11/11] bcache: fix input overflow to cache set sysfs file
 io_error_halflife

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@suse.de>
---
 drivers/md/bcache/sysfs.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 9c80e816de5d..8721e2f5fff6 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -792,8 +792,14 @@ STORE(__bch_cache_set)
 	sysfs_strtoul_clamp(io_error_limit, c->error_limit, 0, UINT_MAX);
 
 	/* 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) {
+		long v;
+
+		v = strtoul_safe_clamp(buf, v, 0, UINT_MAX);
+		if (v < 0)
+			return v;
+		c->error_decay = v / 88;
+	}
 
 	if (attr == &sysfs_io_disable) {
 		v = strtoul_or_return(buf);
-- 
2.16.4