[PATCH 28/88] sysctl: fix null checking in bin_dn_node_address()

[Luis Henriques]

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

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

From: Xi Wang <xi.wang at gmail.com>

commit df1778be1a33edffa51d094eeda87c858ded6560 upstream.

The null check of `strchr() + 1' is broken, which is always non-null,
leading to OOB read.  Instead, check the result of strchr().

Signed-off-by: Xi Wang <xi.wang at gmail.com>
Cc: "Eric W. Biederman" <ebiederm at xmission.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/sysctl_binary.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index a650694..9f9aa32 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1194,9 +1194,10 @@ static ssize_t bin_dn_node_address(struct file *file,
 
 		/* Convert the decnet address to binary */
 		result = -EIO;
-		nodep = strchr(buf, '.') + 1;
+		nodep = strchr(buf, '.');
 		if (!nodep)
 			goto out;
+		++nodep;
 
 		area = simple_strtoul(buf, NULL, 10);
 		node = simple_strtoul(nodep, NULL, 10);
-- 
1.8.1.2