From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7466169942; Wed, 21 Feb 2024 13:51:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708523500; cv=none; b=ErrY4hQS/d2db33D1QIpEpsmex/qh2uYjDikt692pkGOV7DuSSotUY3Q/F6fwSNXMHYcGbWkWf6r07TnEA6x3mE2raW/JtzkY9QlC31To/JOECKbrYybhg68XwcrW61Thhan4PGOP3Zu8QPBrgXr3P2VOLPedWSQYWM+4W7CuDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708523500; c=relaxed/simple; bh=MFpTbfxR+LeGBXdJ0uqnF76qRT3/WmXBWCGAJ3Unzvg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r2tV6z6SgLjpxjJORl7mwhEFChJMacn6Et24rXSBLFshKCg6wBPSq62tMFXhtB3ds1Anx5b85JhBig5OZcUz25JjlsPccm9bysCyD44tqMRkWCCpCCqH0L6xIK1dcwLUwfbpD55kel/+sVxlXrENJArRndRfQL23bg3aZyaJBtA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=c+42FlRQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="c+42FlRQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9143FC433C7; Wed, 21 Feb 2024 13:51:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708523499; bh=MFpTbfxR+LeGBXdJ0uqnF76qRT3/WmXBWCGAJ3Unzvg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c+42FlRQXqZ3Qm5kgLOETay63U+WC3mxXpm0W7isUKsOrPpmQmPVi810iTnP+NCDT Ckqw3D7vBCyqYDehLbROTpM22uzoGvTS4GPsBExAwPNxZ66xqM1sNYgaOa6KnCASqo 4DUI9gG9idxizhT5QxMK2e/SfBmPGuac7Hjt2d+Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+4fa4a2d1f5a5ee06f006@syzkaller.appspotmail.com, Kuniyuki Iwashima , Paolo Abeni Subject: [PATCH 5.15 425/476] af_unix: Fix task hung while purging oob_skb in GC. Date: Wed, 21 Feb 2024 14:07:56 +0100 Message-ID: <20240221130023.744628309@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221130007.738356493@linuxfoundation.org> References: <20240221130007.738356493@linuxfoundation.org> User-Agent: quilt/0.67 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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuniyuki Iwashima commit 25236c91b5ab4a26a56ba2e79b8060cf4e047839 upstream. syzbot reported a task hung; at the same time, GC was looping infinitely in list_for_each_entry_safe() for OOB skb. [0] syzbot demonstrated that the list_for_each_entry_safe() was not actually safe in this case. A single skb could have references for multiple sockets. If we free such a skb in the list_for_each_entry_safe(), the current and next sockets could be unlinked in a single iteration. unix_notinflight() uses list_del_init() to unlink the socket, so the prefetched next socket forms a loop itself and list_for_each_entry_safe() never stops. Here, we must use while() and make sure we always fetch the first socket. [0]: Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 5065 Comm: syz-executor236 Not tainted 6.8.0-rc3-syzkaller-00136-g1f719a2f3fa6 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:26 [inline] RIP: 0010:check_kcov_mode kernel/kcov.c:173 [inline] RIP: 0010:__sanitizer_cov_trace_pc+0xd/0x60 kernel/kcov.c:207 Code: cc cc cc cc 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 65 48 8b 14 25 40 c2 03 00 <65> 8b 05 b4 7c 78 7e a9 00 01 ff 00 48 8b 34 24 74 0f f6 c4 01 74 RSP: 0018:ffffc900033efa58 EFLAGS: 00000283 RAX: ffff88807b077800 RBX: ffff88807b077800 RCX: 1ffffffff27b1189 RDX: ffff88802a5a3b80 RSI: ffffffff8968488d RDI: ffff88807b077f70 RBP: ffffc900033efbb0 R08: 0000000000000001 R09: fffffbfff27a900c R10: ffffffff93d48067 R11: ffffffff8ae000eb R12: ffff88807b077800 R13: dffffc0000000000 R14: ffff88807b077e40 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000564f4fc1e3a8 CR3: 000000000d57a000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: unix_gc+0x563/0x13b0 net/unix/garbage.c:319 unix_release_sock+0xa93/0xf80 net/unix/af_unix.c:683 unix_release+0x91/0xf0 net/unix/af_unix.c:1064 __sock_release+0xb0/0x270 net/socket.c:659 sock_close+0x1c/0x30 net/socket.c:1421 __fput+0x270/0xb80 fs/file_table.c:376 task_work_run+0x14f/0x250 kernel/task_work.c:180 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0xa8a/0x2ad0 kernel/exit.c:871 do_group_exit+0xd4/0x2a0 kernel/exit.c:1020 __do_sys_exit_group kernel/exit.c:1031 [inline] __se_sys_exit_group kernel/exit.c:1029 [inline] __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1029 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xd5/0x270 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x6f/0x77 RIP: 0033:0x7f9d6cbdac09 Code: Unable to access opcode bytes at 0x7f9d6cbdabdf. RSP: 002b:00007fff5952feb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f9d6cbdac09 RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000 RBP: 00007f9d6cc552b0 R08: ffffffffffffffb8 R09: 0000000000000006 R10: 0000000000000006 R11: 0000000000000246 R12: 00007f9d6cc552b0 R13: 0000000000000000 R14: 00007f9d6cc55d00 R15: 00007f9d6cbabe70 Reported-by: syzbot+4fa4a2d1f5a5ee06f006@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=4fa4a2d1f5a5ee06f006 Fixes: 1279f9d9dec2 ("af_unix: Call kfree_skb() for dead unix_(sk)->oob_skb in GC.") Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20240209220453.96053-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman --- net/unix/garbage.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -315,10 +315,11 @@ void unix_gc(void) __skb_queue_purge(&hitlist); #if IS_ENABLED(CONFIG_AF_UNIX_OOB) - list_for_each_entry_safe(u, next, &gc_candidates, link) { - struct sk_buff *skb = u->oob_skb; + while (!list_empty(&gc_candidates)) { + u = list_entry(gc_candidates.next, struct unix_sock, link); + if (u->oob_skb) { + struct sk_buff *skb = u->oob_skb; - if (skb) { u->oob_skb = NULL; kfree_skb(skb); }