[Bug 208173] New: BUG: using smp_processor_id() in preemptible, caller is ext4_mb_new_blocks

[Bug 208173] New: BUG: using smp_processor_id() in preemptible, caller is ext4_mb_new_blocks

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208173

            Bug ID: 208173
           Summary: BUG: using smp_processor_id() in preemptible, caller
                    is ext4_mb_new_blocks
           Product: File System
           Version: 2.5
    Kernel Version: 5.8.0-rc1
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: fs_ext4@kernel-bugs.osdl.org
          Reporter: tseewald@gmail.com
        Regression: No

Created attachment 289655
  --> https://bugzilla.kernel.org/attachment.cgi?id=289655&action=edit
dmesg

Immediately after booting 5.8.0-rc1 and logging in, dmesg is filled with BUG
backtraces like:

[   10.823091] BUG: using smp_processor_id() in preemptible [00000000] code:
auditd/788
[   10.823095] caller is ext4_mb_new_blocks+0x285/0xd50
[   10.823096] CPU: 2 PID: 788 Comm: auditd Not tainted 5.8.0-rc1 #15
[   10.823097] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z77
Extreme4, BIOS P2.90 07/11/2013
[   10.823097] Call Trace:
[   10.823104]  dump_stack+0x57/0x70
[   10.823107]  check_preemption_disabled+0xab/0xc0
[   10.823109]  ext4_mb_new_blocks+0x285/0xd50
[   10.823112]  ? __kmalloc+0x1ac/0x280
[   10.823114]  ? ext4_find_extent+0x2a1/0x370
[   10.823116]  ? ext4_find_extent+0x163/0x370
[   10.823118]  ? release_pages+0x3b1/0x470
[   10.823120]  ext4_ext_map_blocks+0x84d/0xcc0
[   10.823122]  ext4_map_blocks+0xef/0x560
[   10.823124]  ? kmem_cache_alloc+0x181/0x220
[   10.823126]  ext4_writepages+0x856/0xe00
[   10.823130]  ? futex_wait+0x11d/0x210
[   10.823132]  ? do_writepages+0x41/0xd0
[   10.823134]  ? __ext4_mark_inode_dirty+0x250/0x250
[   10.823134]  do_writepages+0x41/0xd0
[   10.823137]  ? wbc_attach_and_unlock_inode+0xd6/0x140
[   10.823139]  __filemap_fdatawrite_range+0xcb/0x100
[   10.823141]  file_write_and_wait_range+0x5e/0xb0
[   10.823143]  ext4_sync_file+0x10c/0x3a0
[   10.823144]  do_fsync+0x38/0x70
[   10.823146]  __x64_sys_fsync+0x10/0x20
[   10.823147]  do_syscall_64+0x47/0x80
[   10.823150]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   10.823152] RIP: 0033:0x7fb904384f1b
[   10.823152] Code: Bad RIP value.
[   10.823153] RSP: 002b:00007fb903d4cd00 EFLAGS: 00000293 ORIG_RAX:
000000000000004a
[   10.823154] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
00007fb904384f1b
[   10.823155] RDX: 0000000000000001 RSI: 0000000000000081 RDI:
0000000000000005
[   10.823155] RBP: 000055c4f63e82c0 R08: 0000000000000000 R09:
00007fb903d4d700
[   10.823156] R10: 0000000000000000 R11: 0000000000000293 R12:
00007ffd56550cce
[   10.823156] R13: 00007ffd56550ccf R14: 00007ffd56550cd0 R15:
00007fb903d4d700

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[Bug 208173] BUG: using smp_processor_id() in preemptible, caller is ext4_mb_new_blocks

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208173

--- Comment #1 from Tom Seewald (tseewald@gmail.com) ---
Created attachment 289657
  --> https://bugzilla.kernel.org/attachment.cgi?id=289657&action=edit
kernel config

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[Bug 208173] BUG: using smp_processor_id() in preemptible, caller is ext4_mb_new_blocks

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208173

Theodore Tso (tytso@mit.edu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tytso@mit.edu
         Resolution|---                         |CODE_FIX

--- Comment #2 from Theodore Tso (tytso@mit.edu) ---
Fixed in [1]

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=811985365378df01386c3cfb7ff716e74ca376d5

Which unfortunately just missed getting included in 5.8-rc1.

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[Bug 208173] BUG: using smp_processor_id() in preemptible, caller is ext4_mb_new_blocks

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=208173

--- Comment #3 from Tom Seewald (tseewald@gmail.com) ---
After looking around, syzkaller already found this bug [1], and a fix was
already posted [2] but Linus didn't pull it before tagging the rc1 release.

I manually applied commit 811985365378df01386c3cfb7ff716e74ca376d5 ("ext4:
mballoc: Use this_cpu_read instead of this_cpu_ptr") from
https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git, and I can
confirm that this fixes the problem. Hopefully this makes it in by rc2.

I'll close this report once Linus pulls the fix.

[1]
https://syzkaller.appspot.com/bug?id=b7f459091a40a67a13f27d2281281ffd0ed8e5e1
[2] https://lore.kernel.org/lkml/20200614200034.GA3294624@mit.edu/T/

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