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Subject: Re: general protection fault in ext4_writepages
To:     syzbot <syzbot+9567fda428fba259deba@syzkaller.appspotmail.com>,
        adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        tytso@mit.edu, Jan Kara <jack@suse.cz>
References: <00000000000073d3a70597069799@google.com>
 <20191111051236.2717D11C05B@d06av25.portsmouth.uk.ibm.com>
Cc:     Ritesh Harjani <riteshh@linux.ibm.com>
From:   Ritesh Harjani <riteshh@linux.ibm.com>
Date:   Mon, 11 Nov 2019 11:02:31 +0530
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Updating the link.

On 11/11/19 10:42 AM, Ritesh Harjani wrote:
> Hello Ted,
> 
> This issue seems to be coming via fault injection failure in slab
> allocation. This should be fixed via below patch on your latest ext4
> branch.
> 
> https://marc.info/?l=linux-ext4&m=804&w=2
https://marc.info/?l=linux-ext4&m=157303310723804&w=2


> 
> Please let me know if anything else is needed.
> 
> -ritesh
> 
> On 11/11/19 5:14 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit:    dcd34bd2 Add linux-next specific files for 20191106
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=11a0a4fce00000
>> kernel config:  
>> https://syzkaller.appspot.com/x/.config?x=742545dcdea21726
>> dashboard link: 
>> https://syzkaller.appspot.com/bug?extid=9567fda428fba259deba
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>> syz repro:      
>> https://syzkaller.appspot.com/x/repro.syz?x=1645c42ce00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1108a23ae00000
>>
>> The bug was bisected to:
>>
>> commit c8cc88163f40df39e50cda63ac361631864b453e
>> Author: Ritesh Harjani <riteshh@linux.ibm.com>
>> Date:   Wed Oct 16 07:37:10 2019 +0000
>>
>>      ext4: Add support for blocksize < pagesize in dioread_nolock
>>
>> bisection log:  
>> https://syzkaller.appspot.com/x/bisect.txt?x=1044c6b4e00000
>> final crash:    
>> https://syzkaller.appspot.com/x/report.txt?x=1244c6b4e00000
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1444c6b4e00000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the 
>> commit:
>> Reported-by: syzbot+9567fda428fba259deba@syzkaller.appspotmail.com
>> Fixes: c8cc88163f40 ("ext4: Add support for blocksize < pagesize in 
>> dioread_nolock")
>>
>> RDX: 0000000000000000 RSI: 0000000100000003 RDI: 0000000000000003
>> RBP: 0000000000000004 R08: 0000000000000001 R09: 00007fffd7a50033
>> R10: 0000000028120001 R11: 0000000000000246 R12: 0000000000401ef0
>> R13: 0000000000401f80 R14: 0000000000000000 R15: 0000000000000000
>> kasan: CONFIG_KASAN_INLINE enabled
>> kasan: GPF could be caused by NULL-ptr deref or user memory access
>> general protection fault: 0000 [#1] PREEMPT SMP KASAN
>> CPU: 0 PID: 8639 Comm: syz-executor031 Not tainted 
>> 5.4.0-rc6-next-20191106 #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, 
>> BIOS Google 01/01/2011
>> RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2557 [inline]
>> RIP: 0010:ext4_writepages+0x17b4/0x2e80 fs/ext4/inode.c:2911
>> Code: ff ff e8 1f cf b0 ff 48 8b 85 30 fe ff ff 48 8b 8d 00 fe ff ff 
>> 48 8d 78 10 48 89 fa 48 c1 ea 03 0f b6 89 c2 00 00 00 48 d3 e3 <42> 80 
>> 3c 2a 00 0f 85 03 16 00 00 48 89 58 10 48 c7 c0 08 ad c4 89
>> RSP: 0018:ffff88808bf77890 EFLAGS: 00010206
>> RAX: fffffffffffffff4 RBX: 00000000007ff000 RCX: 000000000000000c
>> RDX: 0000000000000000 RSI: ffffffff820534cd RDI: 0000000000000004
>> RBP: ffff88808bf77ac0 R08: 0000000000000000 R09: ffffed1015d06b7d
>> R10: ffffed1015d06b7c R11: ffff8880ae835be3 R12: 0000000000000000
>> R13: dffffc0000000000 R14: 00000000000007ff R15: ffff888086499488
>> FS:  0000000001162880(0000) GS:ffff8880ae800000(0000) 
>> knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000000 CR3: 000000009366b000 CR4: 00000000001406f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>   ? 0xffffffff81000000
>>   do_writepages+0xfa/0x2a0 mm/page-writeback.c:2344
>>   __filemap_fdatawrite_range+0x2bc/0x3b0 mm/filemap.c:421
>>   filemap_write_and_wait_range mm/filemap.c:681 [inline]
>>   filemap_write_and_wait_range+0xfc/0x1d0 mm/filemap.c:675
>>   ext4_punch_hole+0x27d/0x1320 fs/ext4/inode.c:4314
>>   ext4_fallocate+0x419/0x2470 fs/ext4/extents.c:4889
>>   vfs_fallocate+0x4aa/0xa50 fs/open.c:309
>>   ksys_fallocate+0x58/0xa0 fs/open.c:332
>>   __do_sys_fallocate fs/open.c:340 [inline]
>>   __se_sys_fallocate fs/open.c:338 [inline]
>>   __x64_sys_fallocate+0x97/0xf0 fs/open.c:338
>>   do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x440609
>> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007fffd7a50c58 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
>> RAX: ffffffffffffffda RBX: 00007fffd7a50c60 RCX: 0000000000440609
>> RDX: 0000000000000000 RSI: 0000000100000003 RDI: 0000000000000003
>> RBP: 0000000000000004 R08: 0000000000000001 R09: 00007fffd7a50033
>> R10: 0000000028120001 R11: 0000000000000246 R12: 0000000000401ef0
>> R13: 0000000000401f80 R14: 0000000000000000 R15: 0000000000000000
>> Modules linked in:
>> ---[ end trace 0ee46d2ea32148f5 ]---
>> RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2557 [inline]
>> RIP: 0010:ext4_writepages+0x17b4/0x2e80 fs/ext4/inode.c:2911
>> Code: ff ff e8 1f cf b0 ff 48 8b 85 30 fe ff ff 48 8b 8d 00 fe ff ff 
>> 48 8d 78 10 48 89 fa 48 c1 ea 03 0f b6 89 c2 00 00 00 48 d3 e3 <42> 80 
>> 3c 2a 00 0f 85 03 16 00 00 48 89 58 10 48 c7 c0 08 ad c4 89
>> RSP: 0018:ffff88808bf77890 EFLAGS: 00010206
>> RAX: fffffffffffffff4 RBX: 00000000007ff000 RCX: 000000000000000c
>> RDX: 0000000000000000 RSI: ffffffff820534cd RDI: 0000000000000004
>> RBP: ffff88808bf77ac0 R08: 0000000000000000 R09: ffffed1015d06b7d
>> R10: ffffed1015d06b7c R11: ffff8880ae835be3 R12: 0000000000000000
>> R13: dffffc0000000000 R14: 00000000000007ff R15: ffff888086499488
>> FS:  0000000001162880(0000) GS:ffff8880ae800000(0000) 
>> knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 0000000000000000 CR3: 000000009366b000 CR4: 00000000001406f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>
>>
>> ---
>> This bug 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 bug report. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>> For information about bisection process see: 
>> https://goo.gl/tpsmEJ#bisection
>> syzbot can test patches for this bug, for details see:
>> https://goo.gl/tpsmEJ#testing-patches
>