New: [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

Bug 66881 [email protected] 1 participant 6 messages Dec 12, 2013 – Mar 31, 2014

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author

2013-12-12 04:56 UTC #0 lore raw

https://bugzilla.kernel.org/show_bug.cgi?id=66881

            Bug ID: 66881
           Summary: [3.12.1][ext4]kernel BUG at
                    fs/ext4/extents_status.c:709!
           Product: File System
           Version: 2.5
    Kernel Version: 3.12.1
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: [email protected]
          Reporter: [email protected]
        Regression: No

With 'fsfuzz - file system fuzzer' found the following kernel bug:

[  416.118860] ------------[ cut here ]------------
[  416.118865] kernel BUG at fs/ext4/extents_status.c:709!
[  416.118909] illegal operation: 0001 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[  416.118915] Modules linked in: loop dm_multipath scsi_dh dm_mod vmur autofs4
[  416.118925] CPU: 0 PID: 798 Comm: fstest Not tainted 3.12.1 #1
[  416.118928] task: 000000003c3b4b20 ti: 000000003d0b8000 task.ti:
000000003d0b8000
[  416.118939] Krnl PSW : 0704d00180000000 00000000003c68ec
(ext4_es_cache_extent+0x144/0x1e8)
[  416.118942]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0
EA:3
Krnl GPRS: 0000000000000000 0000000000000020 000000003c44c950 000000000000ae56
[  416.118947]            00000000ffff798a 1fffffffffffffff 1000000000000000
000000003688a848
[  416.118950]            0000000000000020 000000003688a854 000000000000ae56
00000000ffff798a
[  416.118952]            000000003c44c950 00000000000027df 000000003d0bb648
000000003d0bb5c0
[  416.118962] Krnl Code: 00000000003c68e2: 15da                clr    
%r13,%r10
           00000000003c68e4: a7a40004           brc     10,3c68ec
          #00000000003c68e8: a7f40001           brc     15,3c68ea
          >00000000003c68ec: 41b0c488           la      %r11,1160(%r12)
           00000000003c68f0: b904002b           lgr     %r2,%r11
           00000000003c68f4: c0e5001ad134       brasl   %r14,720b5c
           00000000003c68fa: 4120c478           la      %r2,1144(%r12)
           00000000003c68fe: b904003a           lgr     %r3,%r10
[  416.118987] Call Trace:
[  416.118990] ([<00000000003c6930>] ext4_es_cache_extent+0x188/0x1e8)
[  416.118993]  [<00000000003a69c6>] __read_extent_tree_block+0x2de/0x410
[  416.118996]  [<00000000003a793c>] ext4_ext_find_extent+0x210/0x43c
[  416.118998]  [<00000000003acf12>] ext4_ext_map_blocks+0x196/0x1d30
[  416.119002]  [<0000000000379e06>] ext4_map_blocks+0xfe/0x544
[  416.119005]  [<000000000037c0f8>] _ext4_get_block+0xf4/0x1e0
[  416.119009]  [<00000000002f5574>] do_mpage_readpage+0x220/0x770
[  416.119012]  [<00000000002f5b76>] mpage_readpages+0xb2/0x11c
[  416.119016]  [<000000000024648e>] __do_page_cache_readahead+0x292/0x34c
[  416.119019]  [<000000000024685a>] ra_submit+0x42/0x54
[  416.119021]  [<0000000000246ea8>] page_cache_sync_readahead+0x70/0x80
[  416.119025]  [<0000000000239450>] generic_file_aio_read+0x308/0x8ac
[  416.119029]  [<00000000002a78b6>] do_sync_read+0x7e/0xac
[  416.119032]  [<00000000002a885c>] vfs_read+0x98/0x16c
[  416.119035]  [<00000000002a8b32>] SyS_read+0x5e/0x9c
[  416.119039]  [<0000000000721efc>] sysc_nr_ok+0x22/0x28
[  416.119042]  [<000003fffd147e98>] 0x3fffd147e98
[  416.119044] INFO: lockdep is turned off.
[  416.119046] Last Breaking-Event-Address:
[  416.119048]  [<00000000003c68e8>] ext4_es_cache_extent+0x140/0x1e8
[  416.119052]
[  416.119055] Kernel panic - not syncing: Fatal exception: panic_on_oops

And the reason is:
from v3.12.1/fs/ext4/extents.c
...
506 if (prev && (prev != lblk))
507 ext4_es_cache_extent(inode, prev,
508 lblk - prev, ~0,
509 EXTENT_STATUS_HOLE);

Suggested solution:
There should be extra condition for checking 'prev' can not be bigger than 'lblk',
because the difference is passed to 'ext4_es_cache_extent' as len. And this 'len' is used in other calculations.

v3.12.1/fs/ext4/extents_status.c
...
698 ext4_lblk_t end = lblk + len - 1;
...
706 if (!len)
707 return;
708
709 BUG_ON(end < lblk);
...

Proof:
Here is the calculation from real data:
when,
prev=44630
lblk=10208
prev != lblk condition passed and
len = lblk - prev
len = 10208 - 44630 = -34422
since 'len' is of data type 'ext4_lblk_t' -> '_u32' it overflowed. The variable 'end' is depending on 'len' and it hits the bug at "BUG_ON(end < lblk);" .

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author

2013-12-12 06:55 UTC #1 lore raw

[Bug 66881] [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

https://bugzilla.kernel.org/show_bug.cgi?id=66881

Zheng Liu <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #1 from Zheng Liu <[email protected]> ---
This commit (0826a7e1) has been applied to the latest ext4/dev branch, and will be merged into upstream kernel.

Regards,
- Zheng

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author

2013-12-21 11:55 UTC #2 lore raw

[Bug 66881] [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=66881

--- Comment #2 from R.Nageswara Sastry <[email protected]> --- (In reply to Zheng Liu from comment #1)

Quoted 5 lines

This commit (0826a7e1) has been applied to the latest ext4/dev branch, and will be merged into upstream kernel.
Regards,
- Zheng

Hello Zheng,
Could not found the relevant link to the commit. Requesting to share the same. Thanks in advance.

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author

2013-12-21 12:22 UTC #3 lore raw

[Bug 66881] [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=66881

--- Comment #3 from Zheng Liu <[email protected]> --- (In reply to R.Nageswara Sastry from comment #2)

Quoted 10 lines

(In reply to Zheng Liu from comment #1)
Quoted 5 lines
This commit (0826a7e1) has been applied to the latest ext4/dev branch, and will be merged into upstream kernel.
Regards,
- Zheng
Hello Zheng,
Could not found the relevant link to the commit. Requesting to share the same. Thanks in advance.

Ah, sorry, I forgot to mention that this commit is still under ext4 tree. It doesn't be applied into mainline kernel. So that is why you couldn't find it. Here it is.

https://git.kernel.org/cgit/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=0826a7e1ffac96eaced919fcef9994cff9853ef2

Regards,
- Zheng

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author

2014-03-30 15:53 UTC #4 lore raw

[Bug 66881] [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=66881

Conrad Meyer <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |[email protected]

--- Comment #4 from Conrad Meyer <[email protected]> ---
Merged to Linus' tree in merge commit f41bfc9423aac4e589d2b3bedf26b3c249c61146.

(5946d089379a35dda0e531710b48fca05446a196 for this patch.)

It can be closed...

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author

2014-03-31 20:33 UTC #5 lore raw

[Bug 66881] [3.12.1][ext4]kernel BUG at fs/ext4/extents_status.c:709!

In reply to [email protected]

https://bugzilla.kernel.org/show_bug.cgi?id=66881

Theodore Tso <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]
         Resolution|---                         |CODE_FIX

--- Comment #5 from Theodore Tso <[email protected]> --- Thanks for the reminder that the bug could be closed!

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