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Date:   Sun, 03 Jan 2021 06:19:15 -0800
Message-ID: <000000000000886dbd05b7ffa8db@google.com>
Subject: kernel BUG at mm/page-writeback.c:LINE!
From:   syzbot <syzbot+2fc0712f8f8b8b8fa0ef@syzkaller.appspotmail.com>
To:     akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    139711f0 Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11648e93500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f3e74a3fb99ae2c2
dashboard link: https://syzkaller.appspot.com/bug?extid=2fc0712f8f8b8b8fa0ef
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2fc0712f8f8b8b8fa0ef@syzkaller.appspotmail.com

kernel BUG at mm/page-writeback.c:2241!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 26311 Comm: syz-executor.2 Not tainted 5.11.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:write_cache_pages+0xd06/0x1190 mm/page-writeback.c:2241
Code: 02 00 00 e8 dc 6e da ff 48 c7 c6 80 64 54 89 4c 89 ef e8 0d 04 0b 00 0f 0b 49 c7 c4 c0 77 f7 8e e9 ce f9 ff ff e8 ba 6e da ff <0f> 0b e8 b3 6e da ff 49 8d 5c 24 ff e9 c5 f8 ff ff e8 a4 6e da ff
RSP: 0018:ffffc9000931f850 EFLAGS: 00010212
RAX: 000000000000ac05 RBX: 0000000000008000 RCX: ffffc9000d7c1000
RDX: 0000000000040000 RSI: ffffffff819805d6 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffea0000c0ce07
R10: ffffffff8197fee3 R11: 0000000000000000 R12: ffffea0002762cc8
R13: ffffea0000c0ce00 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007f653a526700(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000052e94c CR3: 0000000015251000 CR4: 0000000000350ee0
Call Trace:
 mpage_writepages+0xd8/0x230 fs/mpage.c:714
 do_writepages+0xec/0x290 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x2a1/0x380 mm/filemap.c:422
 fat_cont_expand+0x169/0x230 fs/fat/file.c:235
 fat_setattr+0xac2/0xf40 fs/fat/file.c:501
 notify_change+0xb60/0x10a0 fs/attr.c:336
 do_truncate+0x134/0x1f0 fs/open.c:64
 do_sys_ftruncate+0x703/0x860 fs/open.c:195
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e299
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f653a525c68 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 000000000045e299
RDX: 0000000000000000 RSI: 0000000000000800 RDI: 0000000000000003
RBP: 000000000119c060 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c034
R13: 00007fff76bf2e8f R14: 00007f653a5269c0 R15: 000000000119c034
Modules linked in:
---[ end trace 23c7a881902c6de9 ]---
RIP: 0010:write_cache_pages+0xd06/0x1190 mm/page-writeback.c:2241
Code: 02 00 00 e8 dc 6e da ff 48 c7 c6 80 64 54 89 4c 89 ef e8 0d 04 0b 00 0f 0b 49 c7 c4 c0 77 f7 8e e9 ce f9 ff ff e8 ba 6e da ff <0f> 0b e8 b3 6e da ff 49 8d 5c 24 ff e9 c5 f8 ff ff e8 a4 6e da ff
RSP: 0018:ffffc9000931f850 EFLAGS: 00010212
RAX: 000000000000ac05 RBX: 0000000000008000 RCX: ffffc9000d7c1000
RDX: 0000000000040000 RSI: ffffffff819805d6 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffea0000c0ce07
R10: ffffffff8197fee3 R11: 0000000000000000 R12: ffffea0002762cc8
R13: ffffea0000c0ce00 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007f653a526700(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f228000 CR3: 0000000015251000 CR4: 0000000000350ee0


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