From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-184.mta0.migadu.com (out-184.mta0.migadu.com [91.218.175.184]) (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 3EB52329361 for ; Thu, 19 Mar 2026 08:05:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.184 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773907553; cv=none; b=fuk5JsWVNgPgQ7DHZ3qe4wmeDYZy9MVstKHgWtveEprFTqf/P8KWfCH08KBKCCbx/qBHaLlWZ5AkvyN3iDRYLTsxgidc0pBtlRrYS2+iB/SAR63ecFVovTM0ztcG9PdIka1nOUFfkvcsnrm8si/ThHU48NLBWClQjXxDjUClrhE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773907553; c=relaxed/simple; bh=zgpKepL7OVCYUMpe8eGxqk69QxKkT842tMiO9brplho=; h=Message-ID:Date:MIME-Version:Subject:To:References:Cc:From: In-Reply-To:Content-Type; b=LD3TmmsaW1ZXlg46ZZm5z79mbFcUbDg9nc7QQMaP0ltunM41r+9q0VFoEBe46dDHJ9xYUNzKfDmuKygRrEe8UsmtWkw62M5G0nsehnCvdnhfUNh0ZADD3AitGz1dO5F/9bRv92fJRNR5jwG23mkIN0aNOVpGKyOQVmuE0+qfodk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=GitlksRg; arc=none smtp.client-ip=91.218.175.184 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="GitlksRg" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773907550; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2NsBe2YEaJhTZhc3cWuMJnWEhWKyY3AOJ8RnT3CIBcs=; b=GitlksRgIxyp42kdSyWrbfk+PNIiKVbuiBUlyvhgwLLqUjruQ6658bKKA1+YonHOvpbrjP +6xQgrPPZQFnunkGcIHgx56iyRpBD3Qk1DXHcx8d2dw49v1ygppUi04SCGRq0VwLsRP8xk Q5awulxr0WqJomswxB1il1Wi6XLrgW0= Date: Thu, 19 Mar 2026 16:05:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [syzbot] [mm?] kernel BUG in collapse_scan_file Content-Language: en-US To: syzbot , david@kernel.org, ljs@kernel.org, willy@infradead.org References: <69bba3c0.050a0220.227207.002b.GAE@google.com> Cc: baolin.wang@linux.alibaba.com, npache@redhat.com, linux-mm@kvack.org, baohua@kernel.org, ryan.roberts@arm.com, syzkaller-bugs@googlegroups.com, dev.jain@arm.com, ziy@nvidia.com, linux-kernel@vger.kernel.org, Liam.Howlett@oracle.com, akpm@linux-foundation.org X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <69bba3c0.050a0220.227207.002b.GAE@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Ccing Willy IIUC, this is a dup of the earlier report[1], which I looked into back in January. The root cause is the same: collapse_file() calls xas_lock_irq() without resetting the xas state first, tripping the XAS_INVALID() assertion: #define xas_lock_irq(xas) xa_lock_irq(XAS_INVALID(xas)->xa) static inline struct xa_state *XAS_INVALID(struct xa_state *xas) { XA_NODE_BUG_ON(xas->xa_node, xas_valid(xas)); return xas; } Added by commit: commit 43b00759f21b10142094d1ae5ff65cbb368953a3 Author: Matthew Wilcox (Oracle) Date: Sun Dec 14 10:53:31 2025 -0500 XArray: Add extra debugging check to xas_lock and friends While tracking down a recent bug, we discovered somewhere that had forgotten to call xas_reset() before calling xas_lock(). Add a debug check to be sure that doesn't happen in future and fix all the places in the test suite which were carelessly doing just this. Suggested-by: Linus Torvalds Signed-off-by: Matthew Wilcox (Oracle) I posted a HACK fix at the time[2], but David pointed out that Willy had mentioned it likely needs more thought[3]. [1] https://lore.kernel.org/all/69757ea0.a00a0220.33ccc7.0017.GAE@google.com/ [2] https://lore.kernel.org/all/20260125121001.32733-1-lance.yang@linux.dev/ [3] https://lore.kernel.org/all/7bce9231-714c-424a-a4e3-dd42734fb767@kernel.org/ Thanks, Lance On 2026/3/19 15:20, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 95c541ddfb08 Add linux-next specific files for 20260316 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=15ccc216580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ed431987028345c6 > dashboard link: https://syzkaller.appspot.com/bug?extid=8961cb270ae74b4129fb > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12f778da580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cc006a580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/c40f27ad73d8/disk-95c541dd.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/bd811888f684/vmlinux-95c541dd.xz > kernel image: https://storage.googleapis.com/syzbot-assets/3b72363d7dbd/bzImage-95c541dd.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+8961cb270ae74b4129fb@syzkaller.appspotmail.com > > node ffff88805d558b00 offset 0 parent ffff88805d558840 shift 0 count 3 values 0 array ffff88807a8195c0 list ffff88805d558b18 ffff88805d558b18 marks 0 0 0 > ------------[ cut here ]------------ > kernel BUG at ./include/linux/xarray.h:1441! > Oops: invalid opcode: 0000 [#1] SMP KASAN PTI > CPU: 0 UID: 0 PID: 6001 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 > RIP: 0010:XAS_INVALID include/linux/xarray.h:1441 [inline] > RIP: 0010:collapse_file mm/khugepaged.c:2055 [inline] > RIP: 0010:collapse_scan_file+0x4f98/0x5230 mm/khugepaged.c:2404 > Code: ff 4c 89 e7 48 c7 c6 60 b2 dc 8b e8 82 62 f1 fe 90 0f 0b 48 85 db 0f 84 03 01 00 00 e8 71 e5 8f ff 48 89 df e8 a9 20 7b 09 90 <0f> 0b e8 61 e5 8f ff 48 89 df 48 c7 c6 60 b2 dc 8b e8 52 62 f1 fe > RSP: 0018:ffffc90003826e20 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffff88805d558b00 RCX: a13f20bd39c5a100 > RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 > RBP: ffffc90003827130 R08: ffffc90003826ba7 R09: 1ffff92000704d74 > R10: dffffc0000000000 R11: fffff52000704d75 R12: ffffea0001b678f0 > R13: dffffc0000000000 R14: 0000000000000000 R15: ffffc90003827010 > FS: 000055557e3c2500(0000) GS:ffff888125437000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000020000000b000 CR3: 000000007ac66000 CR4: 00000000003526f0 > Call Trace: > > collapse_single_pmd+0x22b/0x4510 mm/khugepaged.c:2437 > madvise_collapse+0x34c/0x820 mm/khugepaged.c:2859 > madvise_vma_behavior+0x1094/0x4460 mm/madvise.c:1362 > madvise_walk_vmas+0x573/0xae0 mm/madvise.c:1711 > madvise_do_behavior+0x386/0x540 mm/madvise.c:1927 > do_madvise+0x1fa/0x2e0 mm/madvise.c:2020 > __do_sys_madvise mm/madvise.c:2029 [inline] > __se_sys_madvise mm/madvise.c:2027 [inline] > __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2027 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f90d419c799 > Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007ffd50711398 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > RAX: ffffffffffffffda RBX: 00007f90d4415fa0 RCX: 00007f90d419c799 > RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000200000000000 > RBP: 00007f90d4232c99 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007f90d4415fac R14: 00007f90d4415fa0 R15: 00007f90d4415fa0 > > Modules linked in: > ---[ end trace 0000000000000000 ]--- > RIP: 0010:XAS_INVALID include/linux/xarray.h:1441 [inline] > RIP: 0010:collapse_file mm/khugepaged.c:2055 [inline] > RIP: 0010:collapse_scan_file+0x4f98/0x5230 mm/khugepaged.c:2404 > Code: ff 4c 89 e7 48 c7 c6 60 b2 dc 8b e8 82 62 f1 fe 90 0f 0b 48 85 db 0f 84 03 01 00 00 e8 71 e5 8f ff 48 89 df e8 a9 20 7b 09 90 <0f> 0b e8 61 e5 8f ff 48 89 df 48 c7 c6 60 b2 dc 8b e8 52 62 f1 fe > RSP: 0018:ffffc90003826e20 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffff88805d558b00 RCX: a13f20bd39c5a100 > RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 > RBP: ffffc90003827130 R08: ffffc90003826ba7 R09: 1ffff92000704d74 > R10: dffffc0000000000 R11: fffff52000704d75 R12: ffffea0001b678f0 > R13: dffffc0000000000 R14: 0000000000000000 R15: ffffc90003827010 > FS: 000055557e3c2500(0000) GS:ffff888125537000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f8156602000 CR3: 000000007ac66000 CR4: 00000000003526f0 > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup