Re: KASAN: stack-out-of-bounds Write in read_extent_buffer

[Johannes Thumshirn]

On 21/09/2020 16:32, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    860461e4 Add linux-next specific files for 20200917
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=141fc5d9900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f2392812d6c63d5c
> dashboard link: https://syzkaller.appspot.com/bug?extid=1d393803acac53c985a0
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16778b07900000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1216f8ad900000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1d393803acac53c985a0@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ==================================================================
> BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:399 [inline]
> BUG: KASAN: stack-out-of-bounds in read_extent_buffer+0x114/0x150 fs/btrfs/extent_io.c:5674
> Write of size 8 at addr ffffc90000dd79f0 by task kworker/u4:1/21
> 
> CPU: 1 PID: 21 Comm: kworker/u4:1 Not tainted 5.9.0-rc5-next-20200917-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: btrfs-endio-meta btrfs_work_helper
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x198/0x1fb lib/dump_stack.c:118
>  print_address_description.constprop.0.cold+0x5/0x497 mm/kasan/report.c:385
>  __kasan_report mm/kasan/report.c:545 [inline]
>  kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
>  check_memory_region_inline mm/kasan/generic.c:186 [inline]
>  check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
>  memcpy+0x39/0x60 mm/kasan/common.c:106
>  memcpy include/linux/string.h:399 [inline]
>  read_extent_buffer+0x114/0x150 fs/btrfs/extent_io.c:5674
>  btree_readpage_end_io_hook+0x7de/0x950 fs/btrfs/disk-io.c:641
>  end_bio_extent_readpage+0x4de/0x10c0 fs/btrfs/extent_io.c:2854
>  bio_endio+0x3d3/0x7a0 block/bio.c:1449
>  end_workqueue_fn+0x114/0x170 fs/btrfs/disk-io.c:1696
>  btrfs_work_helper+0x20a/0xd20 fs/btrfs/async-thread.c:318
>  process_one_work+0x933/0x15a0 kernel/workqueue.c:2269
>  worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
>  kthread+0x3af/0x4a0 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
> 
> 
> addr ffffc90000dd79f0 is located in stack of task kworker/u4:1/21 at offset 48 in frame:
>  btree_readpage_end_io_hook+0x0/0x950 fs/btrfs/disk-io.c:201
> 
> this frame has 4 objects:
>  [48, 52) 'val'
>  [64, 80) 'fsid'
>  [96, 128) 'result'
>  [160, 192) 'found'
> 
> Memory state around the buggy address:
>  ffffc90000dd7880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffc90000dd7900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> ffffc90000dd7980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f1 f1 04 f2
>                                                              ^
>  ffffc90000dd7a00: 00 00 f2 f2 00 00 00 00 f2 f2 f2 f2 00 00 00 00
>  ffffc90000dd7a80: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================
> 
> 
> ---
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> 
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> 

#syz test: git://github.com/kdave/btrfs-devel.git misc-5.9