From: Pietro Borrello <borrello@diag.uniroma1.it>

Date: Sat, 4 Feb 2023 17:39:22 +0000

Subject: tap: tap_open(): correctly initialize socket uid

Git-commit: 66b2c338adce580dfce2199591e65e2bab889cff

Patch-mainline: v6.3-rc1

References: CVE-2023-1076 bsc#1208599

sock_init_data() assumes that the `struct socket` passed in input is

contained in a `struct socket_alloc` allocated with sock_alloc().

However, tap_open() passes a `struct socket` embedded in a `struct

tap_queue` allocated with sk_alloc().

This causes a type confusion when issuing a container_of() with

SOCK_INODE() in sock_init_data() which results in assigning a wrong

sk_uid to the `struct sock` in input.

On default configuration, the type confused field overlaps with

padding bytes between `int vnet_hdr_sz` and `struct tap_dev __rcu

*tap` in `struct tap_queue`, which makes the uid of all tap sockets 0,

i.e., the root one.

Fix the assignment by using sock_init_data_uid().

Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")

Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Signed-off-by: David S. Miller <davem@davemloft.net>

Acked-by: Miroslav Franc <mfranc@suse.cz>

---

 drivers/net/tap.c | 2 +-

 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c

index a2be1994b389..8941aa199ea3 100644

--- a/drivers/net/tap.c

+++ b/drivers/net/tap.c

@@ -533,7 +533,7 @@ static int tap_open(struct inode *inode, struct file *file)

 	q->sock.state = SS_CONNECTED;

 	q->sock.file = file;

 	q->sock.ops = &tap_socket_ops;

-	sock_init_data(&q->sock, &q->sk);

+	sock_init_data_uid(&q->sock, &q->sk, inode->i_uid);

 	q->sk.sk_write_space = tap_sock_write_space;

 	q->sk.sk_destruct = tap_sock_destruct;

 	q->flags = IFF_VNET_HDR | IFF_NO_PI | IFF_TAP;