From: Laszlo Ersek lersek@redhat.com

stable inclusion from stable-v5.10.189 commit 5ea23f1cb67e4468db7ff651627892c9217fec24 category: bugfix bugzilla: 189104, https://gitee.com/src-openeuler/kernel/issues/I7QXHX CVE: CVE-2023-4194

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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

commit 9bc3047374d5bec163e83e743709e23753376f0c upstream.

Commit a096ccca6e50 initializes the "sk_uid" field in the protocol socket (struct sock) from the "/dev/net/tun" device node's owner UID. Per original commit 86741ec25462 ("net: core: Add a UID field to struct sock.", 2016-11-04), that's wrong: the idea is to cache the UID of the userspace process that creates the socket. Commit 86741ec25462 mentions socket() and accept(); with "tun", the action that creates the socket is open("/dev/net/tun").

Therefore the device node's owner UID is irrelevant. In most cases, "/dev/net/tun" will be owned by root, so in practice, commit a096ccca6e50 has no observable effect:

- before, "sk_uid" would be zero, due to undefined behavior (CVE-2023-1076),

- after, "sk_uid" would be zero, due to "/dev/net/tun" being owned by root.

What matters is the (fs)UID of the process performing the open(), so cache that in "sk_uid".

Cc: Eric Dumazet edumazet@google.com Cc: Lorenzo Colitti lorenzo@google.com Cc: Paolo Abeni pabeni@redhat.com Cc: Pietro Borrello borrello@diag.uniroma1.it Cc: netdev@vger.kernel.org Cc: stable@vger.kernel.org Fixes: a096ccca6e50 ("tun: tun_chr_open(): correctly initialize socket uid") Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2173435 Signed-off-by: Laszlo Ersek lersek@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Dong Chenchen dongchenchen2@huawei.com --- drivers/net/tun.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c index f8feec522b32..50c2ce392cd1 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -3456,7 +3456,7 @@ static int tun_chr_open(struct inode *inode, struct file * file) tfile->socket.file = file; tfile->socket.ops = &tun_socket_ops;

- sock_init_data_uid(&tfile->socket, &tfile->sk, inode->i_uid); + sock_init_data_uid(&tfile->socket, &tfile->sk, current_fsuid());

tfile->sk.sk_write_space = tun_sock_write_space; tfile->sk.sk_sndbuf = INT_MAX;