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Message-ID: <8eb7c0b3-afc7-4dca-b614-397514a1994b@kernel.dk>
Date: Mon, 12 Feb 2024 10:47:20 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Pengfei Xu <pengfei.xu@...el.com>, Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Pavel Begunkov <asml.silence@...il.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net-next 2/3] af_unix: Remove io_uring code for GC.
On 2/11/24 7:17 PM, Pengfei Xu wrote:
> Hi,
>
> On 2024-01-29 at 11:04:34 -0800, Kuniyuki Iwashima wrote:
>> Since commit 705318a99a13 ("io_uring/af_unix: disable sending
>> io_uring over sockets"), io_uring's unix socket cannot be passed
>> via SCM_RIGHTS, so it does not contribute to cyclic reference and
>> no longer be candidate for garbage collection.
>>
>> Also, commit 6e5e6d274956 ("io_uring: drop any code related to
>> SCM_RIGHTS") cleaned up SCM_RIGHTS code in io_uring.
>>
>> Let's do it in AF_UNIX as well by reverting commit 0091bfc81741
>> ("io_uring/af_unix: defer registered files gc to io_uring release")
>> and commit 10369080454d ("net: reclaim skb->scm_io_uring bit").
>>
>> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
>> ---
>> include/net/af_unix.h | 1 -
>> net/unix/garbage.c | 25 ++-----------------------
>> net/unix/scm.c | 6 ------
>> 3 files changed, 2 insertions(+), 30 deletions(-)
>>
>> diff --git a/include/net/af_unix.h b/include/net/af_unix.h
>> index f045bbd9017d..9e39b2ec4524 100644
>> --- a/include/net/af_unix.h
>> +++ b/include/net/af_unix.h
>> @@ -20,7 +20,6 @@ static inline struct unix_sock *unix_get_socket(struct file *filp)
>> void unix_inflight(struct user_struct *user, struct file *fp);
>> void unix_notinflight(struct user_struct *user, struct file *fp);
>> void unix_destruct_scm(struct sk_buff *skb);
>> -void io_uring_destruct_scm(struct sk_buff *skb);
>> void unix_gc(void);
>> void wait_for_unix_gc(struct scm_fp_list *fpl);
>> struct sock *unix_peer_get(struct sock *sk);
>> diff --git a/net/unix/garbage.c b/net/unix/garbage.c
>> index af676bb8fb67..ce5b5f87b16e 100644
>> --- a/net/unix/garbage.c
>> +++ b/net/unix/garbage.c
>> @@ -184,12 +184,10 @@ static bool gc_in_progress;
>>
>> static void __unix_gc(struct work_struct *work)
>> {
>> - struct sk_buff *next_skb, *skb;
>> - struct unix_sock *u;
>> - struct unix_sock *next;
>> struct sk_buff_head hitlist;
>> - struct list_head cursor;
>> + struct unix_sock *u, *next;
>> LIST_HEAD(not_cycle_list);
>> + struct list_head cursor;
>>
>> spin_lock(&unix_gc_lock);
>>
>> @@ -269,30 +267,11 @@ static void __unix_gc(struct work_struct *work)
>>
>> spin_unlock(&unix_gc_lock);
>>
>> - /* We need io_uring to clean its registered files, ignore all io_uring
>> - * originated skbs. It's fine as io_uring doesn't keep references to
>> - * other io_uring instances and so killing all other files in the cycle
>> - * will put all io_uring references forcing it to go through normal
>> - * release.path eventually putting registered files.
>> - */
>> - skb_queue_walk_safe(&hitlist, skb, next_skb) {
>> - if (skb->destructor == io_uring_destruct_scm) {
>> - __skb_unlink(skb, &hitlist);
>> - skb_queue_tail(&skb->sk->sk_receive_queue, skb);
>> - }
>> - }
>> -
>> /* Here we are. Hitlist is filled. Die. */
>> __skb_queue_purge(&hitlist);
>>
>> spin_lock(&unix_gc_lock);
>>
>> - /* There could be io_uring registered files, just push them back to
>> - * the inflight list
>> - */
>> - list_for_each_entry_safe(u, next, &gc_candidates, link)
>> - list_move_tail(&u->link, &gc_inflight_list);
>> -
>> /* All candidates should have been detached by now. */
>> WARN_ON_ONCE(!list_empty(&gc_candidates));
>>
>> diff --git a/net/unix/scm.c b/net/unix/scm.c
>> index 505e56cf02a2..db65b0ab5947 100644
>> --- a/net/unix/scm.c
>> +++ b/net/unix/scm.c
>> @@ -148,9 +148,3 @@ void unix_destruct_scm(struct sk_buff *skb)
>> sock_wfree(skb);
>> }
>> EXPORT_SYMBOL(unix_destruct_scm);
>> -
>> -void io_uring_destruct_scm(struct sk_buff *skb)
>> -{
>> - unix_destruct_scm(skb);
>> -}
>> -EXPORT_SYMBOL(io_uring_destruct_scm);
>
> Syzkaller found below issue.
> There is WARNING in __unix_gc in v6.8-rc3_internal-devel_hourly-20240205-094544,
> the kernel contains kernel-next patches.
>
> Bisected and found first bad commit:
> "
> 11498715f266 af_unix: Remove io_uring code for GC.
> "
> It's the same patch as above.
It should be fixed by:
commit 1279f9d9dec2d7462823a18c29ad61359e0a007d
Author: Kuniyuki Iwashima <kuniyu@...zon.com>
Date: Sat Feb 3 10:31:49 2024 -0800
af_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.
which is in Linus's tree.
--
Jens Axboe
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