[PATCH] net: compat: fix msg_controllen overflow in scm_detach_fds_compat()

From: Young Xiao
Date: Tue Jun 04 2019 - 08:34:33 EST


There is a missing check between kmsg->msg_controllen and cmlen,
which can possibly lead to overflow.

This bug is similar to vulnerability that was fixed in commit 6900317f5eff
("net, scm: fix PaX detected msg_controllen overflow in scm_detach_fds").

Signed-off-by: Young Xiao <92siuyang@xxxxxxxxx>
---
net/compat.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/compat.c b/net/compat.c
index a031bd3..8e74dfb 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -301,6 +301,8 @@ void scm_detach_fds_compat(struct msghdr *kmsg, struct scm_cookie *scm)
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
cmlen = CMSG_COMPAT_SPACE(i * sizeof(int));
+ if (kmsg->msg_controllen < cmlen)
+ cmlen = kmsg->msg_controllen;
kmsg->msg_control += cmlen;
kmsg->msg_controllen -= cmlen;
}
--
2.7.4