From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 555E43ED5C8; Wed, 20 May 2026 17:39:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779298752; cv=none; b=o5z3E4w3DW3KqrrhWvZ/IHO4wFd0XobLH9+fypNcSWaloGlAeZyykfklktnxUEYJRA4YUPR/jdKKsrFSkL3BM5wfyngGkqI+vKrSo6DWOSIEa0DAo9v4+n42j39HDAlnK0nAoGGqEWYCIT8to2DwYPz0TVKnFxWAx1bmrjl6/FE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779298752; c=relaxed/simple; bh=o4uA3jZfPdcrlAtzokxcMI241NYSuH8+yENBsdeOs3s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aGzMrWlr+RHbzjvGhLF1OB9ov/81jpnjiejDqmhPJVP17bFByMSmsyZUJ0HaYpwTT27gb8WsGJkGgFMzfCitSYluX7FiSQgRoapZHk9r5tyyx2Fd6snx2MEXeqGGn1+4/wGENNr+IZ4gKUKjK/M13UydV0ZYHktQMscxR6Dom7U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Jl+Q8WaS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Jl+Q8WaS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B39A21F000E9; Wed, 20 May 2026 17:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779298751; bh=6WWP/Drqa+B5qzuniIHI7x+vXQCEQbIBXKfQ0M7Cicg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Jl+Q8WaSq/b7Ruq3Xz6GxBbsHLdCJp981D5CZUrprlGH1UzsklzdFQyb4uDPp+u0e 0adC0kFe7btO6PsFYh0Lqs7nQVVrdkMN3WHVbgXVMsPokUT85zq/myUpdIbTEyq3v7 Xd3iOh0+vLmUVV66kUByAc0/g53A8GKPg+ovMwTA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kuniyuki Iwashima , Martin KaFai Lau , Michal Luczaj , Martin KaFai Lau , Jiayuan Chen , Sasha Levin Subject: [PATCH 6.18 488/957] bpf, sockmap: Fix af_unix iter deadlock Date: Wed, 20 May 2026 18:16:11 +0200 Message-ID: <20260520162145.108053093@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162134.554764788@linuxfoundation.org> References: <20260520162134.554764788@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michal Luczaj [ Upstream commit 4d328dd695383224aa750ddee6b4ad40c0f8d205 ] bpf_iter_unix_seq_show() may deadlock when lock_sock_fast() takes the fast path and the iter prog attempts to update a sockmap. Which ends up spinning at sock_map_update_elem()'s bh_lock_sock(): WARNING: possible recursive locking detected test_progs/1393 is trying to acquire lock: ffff88811ec25f58 (slock-AF_UNIX){+...}-{3:3}, at: sock_map_update_elem+0xdb/0x1f0 but task is already holding lock: ffff88811ec25f58 (slock-AF_UNIX){+...}-{3:3}, at: __lock_sock_fast+0x37/0xe0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(slock-AF_UNIX); lock(slock-AF_UNIX); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by test_progs/1393: #0: ffff88814b59c790 (&p->lock){+.+.}-{4:4}, at: bpf_seq_read+0x59/0x10d0 #1: ffff88811ec25fd8 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: bpf_seq_read+0x42c/0x10d0 #2: ffff88811ec25f58 (slock-AF_UNIX){+...}-{3:3}, at: __lock_sock_fast+0x37/0xe0 #3: ffffffff85a6a7c0 (rcu_read_lock){....}-{1:3}, at: bpf_iter_run_prog+0x51d/0xb00 Call Trace: dump_stack_lvl+0x5d/0x80 print_deadlock_bug.cold+0xc0/0xce __lock_acquire+0x130f/0x2590 lock_acquire+0x14e/0x2b0 _raw_spin_lock+0x30/0x40 sock_map_update_elem+0xdb/0x1f0 bpf_prog_2d0075e5d9b721cd_dump_unix+0x55/0x4f4 bpf_iter_run_prog+0x5b9/0xb00 bpf_iter_unix_seq_show+0x1f7/0x2e0 bpf_seq_read+0x42c/0x10d0 vfs_read+0x171/0xb20 ksys_read+0xff/0x200 do_syscall_64+0x6b/0x3a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: 2c860a43dd77 ("bpf: af_unix: Implement BPF iterator for UNIX domain socket.") Suggested-by: Kuniyuki Iwashima Suggested-by: Martin KaFai Lau Signed-off-by: Michal Luczaj Signed-off-by: Martin KaFai Lau Reviewed-by: Jiayuan Chen Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260414-unix-proto-update-null-ptr-deref-v4-2-2af6fe97918e@rbox.co Signed-off-by: Sasha Levin --- net/unix/af_unix.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index a09c732748945..cf022252d521c 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -3773,15 +3773,14 @@ static int bpf_iter_unix_seq_show(struct seq_file *seq, void *v) struct bpf_prog *prog; struct sock *sk = v; uid_t uid; - bool slow; int ret; if (v == SEQ_START_TOKEN) return 0; - slow = lock_sock_fast(sk); + lock_sock(sk); - if (unlikely(sk_unhashed(sk))) { + if (unlikely(sock_flag(sk, SOCK_DEAD))) { ret = SEQ_SKIP; goto unlock; } @@ -3791,7 +3790,7 @@ static int bpf_iter_unix_seq_show(struct seq_file *seq, void *v) prog = bpf_iter_get_info(&meta, false); ret = unix_prog_seq_show(prog, &meta, v, uid); unlock: - unlock_sock_fast(sk, slow); + release_sock(sk); return ret; } -- 2.53.0