Re: [Syzkaller & bisect] There is BUG: unable to handle kernel NULL pointer dereference in xfs_extent_free_diff_items in v6.4-rc3

[Bagas Sanjaya <bagasdotme@gmail.com>]

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On Mon, May 22, 2023 at 10:07:28AM +0800, Pengfei Xu wrote:
> Hi Darrick,
> 
> Greeting!
> There is BUG: unable to handle kernel NULL pointer dereference in
> xfs_extent_free_diff_items in v6.4-rc3:
> 
> Above issue could be reproduced in v6.4-rc3 and v6.4-rc2 kernel in guest.
> 
> Bisected this issue between v6.4-rc2 and v5.11, found the problem commit is:
> "
> f6b384631e1e xfs: give xfs_extfree_intent its own perag reference
> "
> 
> report0, repro.stat and so on detailed info is link: https://github.com/xupengfe/syzkaller_logs/tree/main/230521_043336_xfs_extent_free_diff_items
> Syzkaller reproduced code: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/repro.c
> Syzkaller reproduced prog: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/repro.prog
> Kconfig: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/kconfig_origin
> Bisect info: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/bisect_info.log
> Issue dmesg: https://github.com/xupengfe/syzkaller_logs/blob/main/230521_043336_xfs_extent_free_diff_items/v6.4-rc3_reproduce_dmesg.log
> 
> v6.4-rc3 reproduced info:
> "
> [   91.419498] loop0: detected capacity change from 0 to 65536
> [   91.420095] XFS: attr2 mount option is deprecated.
> [   91.420500] XFS: ikeep mount option is deprecated.
> [   91.422379] XFS (loop0): Deprecated V4 format (crc=0) will not be supported after September 2030.
> [   91.423468] XFS (loop0): Mounting V4 Filesystem d28317a9-9e04-4f2a-be27-e55b4c413ff6
> [   91.428169] XFS (loop0): Ending clean mount
> [   91.429120] XFS (loop0): Quotacheck needed: Please wait.
> [   91.432182] BUG: kernel NULL pointer dereference, address: 0000000000000008
> [   91.432770] #PF: supervisor read access in kernel mode
> [   91.433216] #PF: error_code(0x0000) - not-present page
> [   91.433640] PGD 0 P4D 0 
> [   91.433864] Oops: 0000 [#1] PREEMPT SMP NOPTI
> [   91.434232] CPU: 0 PID: 33 Comm: kworker/u4:2 Not tainted 6.4.0-rc3-kvm #2
> [   91.434793] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> [   91.435445] Workqueue: xfs_iwalk-393 xfs_pwork_work
> [   91.435855] RIP: 0010:xfs_extent_free_diff_items+0x27/0x40
> [   91.436312] Code: 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 55 48 89 e5 41 54 49 89 f4 53 48 89 d3 e8 05 73 7d ff 49 8b 44 24 28 48 8b 53 28 5b 41 5c <8b> 40 08 5d 2b 42 08 c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00
> [   91.437812] RSP: 0000:ffffc9000012b8c0 EFLAGS: 00010246
> [   91.438250] RAX: 0000000000000000 RBX: ffff8880015826c8 RCX: ffffffff81d71e41
> [   91.438840] RDX: 0000000000000000 RSI: ffff888001ca4800 RDI: 0000000000000002
> [   91.439430] RBP: ffffc9000012b8c0 R08: ffffc9000012b8e0 R09: 0000000000000000
> [   91.440019] R10: ffff88800613f290 R11: ffffffff83e426c0 R12: ffff888001582230
> [   91.440610] R13: ffff888001582428 R14: ffffffff81b042c0 R15: ffffc9000012b908
> [   91.441202] FS:  0000000000000000(0000) GS:ffff88807ec00000(0000) knlGS:0000000000000000
> [   91.441864] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   91.442343] CR2: 0000000000000008 CR3: 000000000ed22006 CR4: 0000000000770ef0
> [   91.442941] PKRU: 55555554
> [   91.443178] Call Trace:
> [   91.443394]  <TASK>
> [   91.443585]  list_sort+0xb8/0x3a0
> [   91.443885]  xfs_extent_free_create_intent+0xb6/0xc0
> [   91.444312]  xfs_defer_create_intents+0xc3/0x220
> [   91.444711]  ? write_comp_data+0x2f/0x90
> [   91.445056]  xfs_defer_finish_noroll+0x9e/0xbc0
> [   91.445449]  ? list_sort+0x344/0x3a0
> [   91.445768]  __xfs_trans_commit+0x4be/0x630
> [   91.446135]  xfs_trans_commit+0x20/0x30
> [   91.446473]  xfs_dquot_disk_alloc+0x45d/0x4e0
> [   91.446860]  xfs_qm_dqread+0x2f7/0x310
> [   91.447192]  xfs_qm_dqget+0xd5/0x300
> [   91.447506]  xfs_qm_quotacheck_dqadjust+0x5a/0x230
> [   91.447921]  xfs_qm_dqusage_adjust+0x249/0x300
> [   91.448313]  xfs_iwalk_ag_recs+0x1bd/0x2e0
> [   91.448671]  xfs_iwalk_run_callbacks+0xc3/0x1c0
> [   91.449071]  xfs_iwalk_ag+0x32e/0x3f0
> [   91.449398]  xfs_iwalk_ag_work+0xbe/0xf0
> [   91.449744]  xfs_pwork_work+0x2c/0xc0
> [   91.450064]  process_one_work+0x3b1/0x860
> [   91.450416]  worker_thread+0x52/0x660
> [   91.450739]  ? __pfx_worker_thread+0x10/0x10
> [   91.451113]  kthread+0x16d/0x1c0
> [   91.451406]  ? __pfx_kthread+0x10/0x10
> [   91.451740]  ret_from_fork+0x29/0x50
> [   91.452064]  </TASK>
> [   91.452261] Modules linked in:
> [   91.452530] CR2: 0000000000000008
> [   91.452819] ---[ end trace 0000000000000000 ]---
> [   91.487979] RIP: 0010:xfs_extent_free_diff_items+0x27/0x40
> [   91.488463] Code: 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 55 48 89 e5 41 54 49 89 f4 53 48 89 d3 e8 05 73 7d ff 49 8b 44 24 28 48 8b 53 28 5b 41 5c <8b> 40 08 5d 2b 42 08 c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00
> [   91.490021] RSP: 0000:ffffc9000012b8c0 EFLAGS: 00010246
> [   91.490472] RAX: 0000000000000000 RBX: ffff8880015826c8 RCX: ffffffff81d71e41
> [   91.491080] RDX: 0000000000000000 RSI: ffff888001ca4800 RDI: 0000000000000002
> [   91.491689] RBP: ffffc9000012b8c0 R08: ffffc9000012b8e0 R09: 0000000000000000
> [   91.492298] R10: ffff88800613f290 R11: ffffffff83e426c0 R12: ffff888001582230
> [   91.492909] R13: ffff888001582428 R14: ffffffff81b042c0 R15: ffffc9000012b908
> [   91.493516] FS:  0000000000000000(0000) GS:ffff88807ec00000(0000) knlGS:0000000000000000
> [   91.494199] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   91.494695] CR2: 0000000000000008 CR3: 000000000ed22006 CR4: 0000000000770ef0
> [   91.495306] PKRU: 55555554
> [   91.495549] note: kworker/u4:2[33] exited with irqs disabled
> "
> 

Thanks for the regression report. I'm adding it to regzbot:

#regzbot ^introduced: f6b384631e1e34
#regzbot title: unable to handle kernel NULL pointer dereference in xfs_extent_free_diff_items (due to xfs_extfree_intent perag change)
#regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=217470

-- 
An old man doll... just what I always wanted! - Clara

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