[RFC PATCH 1/1] net: kcm: Use sk_psock size for kcm_psock_cache

Khalid Masum
2022-07-13T18:14:59Z

`struct sock` has a member `sk_user_data`, which got its memory allocated
in `kcm_attach` by `kcm_psock_cache` with the size of `kcm_psock`. Which
is not enough when the member is used as `sk_psock` causing out of bound
read.

Use `sk_psock` size to allocate memory instead for `sk_user_data`.

Reported-by: syzbot+1fa91bcd05206ff8cbb5@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=1fa91bcd05206ff8cbb5
Signed-off-by: Khalid Masum <khalid.masum.92@gmail.com>

---
net/kcm/kcmsock.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index 71899e5a5a11..688bee56f90c 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -23,6 +23,7 @@
#include <linux/workqueue.h>
#include <linux/syscalls.h>
#include <linux/sched/signal.h>
+#include <linux/skmsg.h>

#include <net/kcm.h>
#include <net/netns/generic.h>
@@ -2041,7 +2042,7 @@ static int __init kcm_init(void)
goto fail;

kcm_psockp = kmem_cache_create("kcm_psock_cache",
- sizeof(struct kcm_psock), 0,
+ sizeof(struct sk_psock), 0,
SLAB_HWCACHE_ALIGN, NULL);
if (!kcm_psockp)
goto fail;
--
2.36.1