2022-01-03 18:47:55

by Shoaib Rao

Subject: Re: [PATCH] af_unix: missing lock releases in af_unix.c

On 1/3/22 05:58, Ryan Cai wrote:
> In method __unix_dgram_recvmsg, the lock u->iolock is not released when skb is true and loop breaks.
>
> Signed-off-by: Ryan Cai <[email protected]>
> ---
> net/unix/af_unix.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index b0bfc78e421c..b97972948d9d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2305,6 +2305,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
> if (skb) {
> if (!(flags & MSG_PEEK))
> scm_stat_del(sk, skb);
> + mutex_unlock(&u->iolock);
> break;
> }
>

It seems to me that the unlock at the end will release the mutex?

out_free:
        skb_free_datagram(sk, skb);
        mutex_unlock(&u->iolock);

Shoaib

2022-01-05 09:19:12

by Ryan Cai

Subject: Re: [PATCH] af_unix: missing lock releases in af_unix.c

Hi, Shoaib

After further checking, the lock is indeed released at the out_free. My patch is invalid. Sorry for the inconvenience.

Best,
Ryan

On 4/1/2022, 2:47 AM, "Shoaib Rao" <[email protected]> wrote:


On 1/3/22 05:58, Ryan Cai wrote:
> In method __unix_dgram_recvmsg, the lock u->iolock is not released when skb is true and loop breaks.
>
> Signed-off-by: Ryan Cai <[email protected]>
> ---
> net/unix/af_unix.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index b0bfc78e421c..b97972948d9d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -2305,6 +2305,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
> if (skb) {
> if (!(flags & MSG_PEEK))
> scm_stat_del(sk, skb);
> + mutex_unlock(&u->iolock);
> break;
> }
>

It seems to me that the unlock at the end will release the mutex?

out_free:
skb_free_datagram(sk, skb);
mutex_unlock(&u->iolock);

Shoaib