From: Laszlo Ersek lersek@redhat.com

stable inclusion from stable-v5.10.189 commit 33a339e717be2c88b7ad11375165168d5b40e38e 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=...

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commit 5c9241f3ceab3257abe2923a59950db0dc8bb737 upstream.

Commit 66b2c338adce initializes the "sk_uid" field in the protocol socket (struct sock) from the "/dev/tapX" 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 "tap", the action that creates the socket is open("/dev/tapX").

Therefore the device node's owner UID is irrelevant. In most cases, "/dev/tapX" will be owned by root, so in practice, commit 66b2c338adce 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/tapX" 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: 66b2c338adce ("tap: tap_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/tap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c index d9018d9fe310..2c9ae02ada3e 100644 --- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -523,7 +523,7 @@ 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_uid(&q->sock, &q->sk, inode->i_uid); + sock_init_data_uid(&q->sock, &q->sk, current_fsuid()); 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;