[PATCH 3.4 060/107] rds: fix an integer overflow test in rds_info_getsockopt()

lizf
2016-03-16T08:28:12Z

From: Dan Carpenter <dan.carpenter@oracle.com>

3.4.111-rc1 review patch. If anyone has any objections, please let me know.

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

commit 468b732b6f76b138c0926eadf38ac88467dcd271 upstream.

"len" is a signed integer. We check that len is not negative, so it
goes from zero to INT_MAX. PAGE_SIZE is unsigned long so the comparison
is type promoted to unsigned long. ULONG_MAX - 4095 is a higher than
INT_MAX so the condition can never be true.

I don't know if this is harmful but it seems safe to limit "len" to
INT_MAX - 4095.

Fixes: a8c879a7ee98 ('RDS: Info and stats')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
net/rds/info.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/info.c b/net/rds/info.c
index 9a6b4f6..140a44a 100644
--- a/net/rds/info.c
+++ b/net/rds/info.c
@@ -176,7 +176,7 @@ int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,

/* check for all kinds of wrapping and the like */
start = (unsigned long)optval;
- if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
+ if (len < 0 || len > INT_MAX - PAGE_SIZE + 1 || start + len < start) {
ret = -EINVAL;
goto out;
}
--
1.9.1