[PATCH 4.19 54/72] net: remove duplicate fetch in sock_getsockopt

Greg Kroah-Hartman
2019-07-02T08:07:38Z

From: JingYi Hou <houjingyi647@gmail.com>

[ Upstream commit d0bae4a0e3d8c5690a885204d7eb2341a5b4884d ]

In sock_getsockopt(), 'optlen' is fetched the first time from userspace.
'len < 0' is then checked. Then in condition 'SO_MEMINFO', 'optlen' is
fetched the second time from userspace.

If change it between two fetches may cause security problems or unexpected
behaivor, and there is no reason to fetch it a second time.

To fix this, we need to remove the second fetch.

Signed-off-by: JingYi Hou <houjingyi647@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/sock.c | 3 ---
1 file changed, 3 deletions(-)

--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1348,9 +1348,6 @@ int sock_getsockopt(struct socket *sock,
{
u32 meminfo[SK_MEMINFO_VARS];

- if (get_user(len, optlen))
- return -EFAULT;
-
sk_get_meminfo(sk, meminfo);

len = min_t(unsigned int, len, sizeof(meminfo));