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 6924923CB; Sat, 4 Jan 2025 18:38:56 +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=1736015936; cv=none; b=rkc+PzR5XXoS6TViPiTfo5XN8uTMqLxjXtIq5QVDrlViCjvjogzCTUB9iqm0rN4PQox67tg1xBdTfQeZn6ePsiUnMQIbY/NmwdtrGfFuD3WPlacmLgJhuXHB1TTgKkoJ9r2Jyf+5jiyd1NWmeJ580aVLFmar3zw5ne2kCg30HVM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736015936; c=relaxed/simple; bh=sMwWst1VaxlfgryvSvavR9svnM6hSEe/ZVod3oQR4RE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XHV036u0HTmASKB2Qq+BaE4xVDfJ7LQrMw3HMWvi7X908wQaKyJQNlzXGw/0iSTrwcCEUEjZ0HFb+7VAfzUwRtviKzcC+VD3XZVCK/+FpaZ2RE/qGjWfj/oiWWLCi3mshNtwAL2PSOZ0n7E40WAS4n+Bph6+h6xmo+A71rvscJ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dTE4UzRP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dTE4UzRP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05EB2C4CED1; Sat, 4 Jan 2025 18:38:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736015936; bh=sMwWst1VaxlfgryvSvavR9svnM6hSEe/ZVod3oQR4RE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dTE4UzRPRnRbYoDiSQnfF56FIybZpAjUD/RxJpmbdcvEFF2r1bv6eCwfhE7QaJg7z VHXd62dYXsXwqWQRHSjXsiQgpOsEo/ydKTT+JLaxsjfAqd13P6AIzhEHKWiYfawbHD 2MFDnZOQ3G/lPyohkDkqVdSC45VXLzmDyrfHYbhnYsqMo+yDgUg1rJvjw4kzPmyWe2 vPugKDlegq+eNacr01FV/tyMzxXYBVnagC/3JUbVR8yA17eDIW0fPV1pvPQpyrQkvJ dPDzu9KBwGDbYbkHUH4iR7yQesPqXnlNc0aaeayGlWzYFuo7QE64D3ZIS/2b1tpKw0 omrjPbAUInb4g== Message-ID: Date: Sat, 4 Jan 2025 19:38:39 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [syzbot] [mptcp?] general protection fault in proc_scheduler To: Eric Dumazet Cc: davem@davemloft.net, geliang@kernel.org, horms@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, martineau@kernel.org, mptcp@lists.linux.dev, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com, syzbot , Al Viro References: <67769ecb.050a0220.3a8527.003f.GAE@google.com> Content-Language: en-GB From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Eric, Thank you for the bug report! On 02/01/2025 16:21, Eric Dumazet wrote: > On Thu, Jan 2, 2025 at 3:12 PM syzbot > wrote: >> >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: ccb98ccef0e5 Merge tag 'platform-drivers-x86-v6.13-4' of g.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=128f6ac4580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=86dd15278dbfe19f >> dashboard link: https://syzkaller.appspot.com/bug?extid=e364f774c6f57f2c86d1 >> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1245eaf8580000 >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/d24eb225cff7/disk-ccb98cce.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/dd81532f8240/vmlinux-ccb98cce.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/18b08e4bbf40/bzImage-ccb98cce.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+e364f774c6f57f2c86d1@syzkaller.appspotmail.com >> >> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] PREEMPT SMP KASAN PTI >> KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] >> CPU: 1 UID: 0 PID: 5924 Comm: syz-executor Not tainted 6.13.0-rc5-syzkaller-00004-gccb98ccef0e5 #0 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 >> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 >> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00 >> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206 >> >> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620 >> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028 >> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040 >> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000 >> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000 >> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Call Trace: >> >> proc_sys_call_handler+0x403/0x5d0 fs/proc/proc_sysctl.c:601 >> __kernel_write_iter+0x318/0xa80 fs/read_write.c:612 >> __kernel_write+0xf6/0x140 fs/read_write.c:632 >> do_acct_process+0xcb0/0x14a0 kernel/acct.c:539 >> acct_pin_kill+0x2d/0x100 kernel/acct.c:192 >> pin_kill+0x194/0x7c0 fs/fs_pin.c:44 >> mnt_pin_kill+0x61/0x1e0 fs/fs_pin.c:81 >> cleanup_mnt+0x3ac/0x450 fs/namespace.c:1366 >> task_work_run+0x14e/0x250 kernel/task_work.c:239 >> exit_task_work include/linux/task_work.h:43 [inline] >> do_exit+0xad8/0x2d70 kernel/exit.c:938 >> do_group_exit+0xd3/0x2a0 kernel/exit.c:1087 >> get_signal+0x2576/0x2610 kernel/signal.c:3017 >> arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337 >> exit_to_user_mode_loop kernel/entry/common.c:111 [inline] >> exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >> __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >> syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218 >> do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7fee3cb87a6a >> Code: Unable to access opcode bytes at 0x7fee3cb87a40. >> RSP: 002b:00007fffcccac688 EFLAGS: 00000202 ORIG_RAX: 0000000000000037 >> RAX: 0000000000000000 RBX: 00007fffcccac710 RCX: 00007fee3cb87a6a >> RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000003 >> RBP: 0000000000000003 R08: 00007fffcccac6ac R09: 00007fffcccacac7 >> R10: 00007fffcccac710 R11: 0000000000000202 R12: 00007fee3cd49500 >> R13: 00007fffcccac6ac R14: 0000000000000000 R15: 00007fee3cd4b000 >> >> Modules linked in: >> ---[ end trace 0000000000000000 ]--- >> RIP: 0010:proc_scheduler+0xc6/0x3c0 net/mptcp/ctrl.c:125 >> Code: 03 42 80 3c 38 00 0f 85 fe 02 00 00 4d 8b a4 24 08 09 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d 7c 24 28 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 cc 02 00 00 4d 8b 7c 24 28 48 8d 84 24 c8 00 00 >> RSP: 0018:ffffc900034774e8 EFLAGS: 00010206 >> RAX: dffffc0000000000 RBX: 1ffff9200068ee9e RCX: ffffc90003477620 >> RDX: 0000000000000005 RSI: ffffffff8b08f91e RDI: 0000000000000028 >> RBP: 0000000000000001 R08: ffffc90003477710 R09: 0000000000000040 >> R10: 0000000000000040 R11: 00000000726f7475 R12: 0000000000000000 >> R13: ffffc90003477620 R14: ffffc90003477710 R15: dffffc0000000000 >> FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007fee3cd452d8 CR3: 000000007d116000 CR4: 00000000003526f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> ---------------- >> Code disassembly (best guess), 1 bytes skipped: >> 0: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1) >> 5: 0f 85 fe 02 00 00 jne 0x309 >> b: 4d 8b a4 24 08 09 00 mov 0x908(%r12),%r12 >> 12: 00 >> 13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax >> 1a: fc ff df >> 1d: 49 8d 7c 24 28 lea 0x28(%r12),%rdi >> 22: 48 89 fa mov %rdi,%rdx >> 25: 48 c1 ea 03 shr $0x3,%rdx >> * 29: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction >> 2d: 0f 85 cc 02 00 00 jne 0x2ff >> 33: 4d 8b 7c 24 28 mov 0x28(%r12),%r15 >> 38: 48 rex.W >> 39: 8d .byte 0x8d >> 3a: 84 24 c8 test %ah,(%rax,%rcx,8) (...) > I thought acct(2) was only allowing regular files. > > acct_on() indeed has : > > if (!S_ISREG(file_inode(file)->i_mode)) { > kfree(acct); > filp_close(file, NULL); > return -EACCES; > } > > It seems there are other ways to call do_acct_process() targeting a sysfs file ? Just to be sure I'm not misunderstanding your comment: do you mean that here, the issue is *not* in MPTCP code where we get the 'struct net' pointer via 'current->nsproxy->net_ns', but in the FS part, right? Here, we have an issue because 'current->nsproxy' is NULL, but is it normal? Or should we simply exit with an error if it is the case because we are in an exiting phase? I'm just a bit confused, because it looks like 'net' is retrieved from different places elsewhere when dealing with sysfs: some get it from 'current' like us, some assign 'net' to 'table->extra2', others get it from 'table->data' (via a container_of()), etc. Maybe we should not use 'current->nsproxy->net_ns' here then? Cheers, Matt -- Sponsored by the NGI0 Core fund.