* [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0
@ 2022-09-27 1:17 Zorro Lang
2022-09-29 21:28 ` Matthew Wilcox
0 siblings, 1 reply; 5+ messages in thread
From: Zorro Lang @ 2022-09-27 1:17 UTC (permalink / raw)
To: linux-mm; +Cc: linuxppc-dev, linux-ext4
Hi mm and ppc list,
Recently I started to hit a kernel panic [2] rarely on *ppc64le* with *1k
blocksize* ext4. It's not easy to reproduce, but still has chance to trigger
by loop running generic/048 on ppc64le (not sure all kind of ppc64le can
reproduce it).
Although I've reported a bug to ext4 [1] (more details refer to [1]), but I only
hit it on ppc64le until now, and I'm not sure if it's an ext4 related bug, more
likes folio related issue, so I cc mm and ppc mail list, hope to get more
reviewing.
Thanks,
Zorro
[1]
https://bugzilla.kernel.org/show_bug.cgi?id=216529
[2]
[ 4638.919160] run fstests generic/048 at 2022-09-23 21:00:41
[ 4641.700564] EXT4-fs (sda3): mounted filesystem with ordered data mode. Quota mode: none.
[ 4641.710999] EXT4-fs (sda3): shut down requested (1)
[ 4641.718544] Aborting journal on device sda3-8.
[ 4641.740342] EXT4-fs (sda3): unmounting filesystem.
[ 4643.000415] EXT4-fs (sda3): mounted filesystem with ordered data mode. Quota mode: none.
[ 4681.230907] BUG: Kernel NULL pointer dereference at 0x00000069
[ 4681.230922] Faulting instruction address: 0xc00000000068ee0c
[ 4681.230929] Oops: Kernel access of bad area, sig: 11 [#1]
[ 4681.230934] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[ 4681.230942] Modules linked in: dm_flakey ext2 dm_snapshot dm_bufio dm_zero dm_mod loop ext4 mbcache jbd2 bonding rfkill tls sunrpc pseries_rng drm fuse drm_panel_orientation_quirks xfs libcrc32c sd_mod t10_pi sg ibmvscsi ibmveth scsi_transport_srp vmx_crypto
[ 4681.230991] CPU: 0 PID: 82 Comm: kswapd0 Kdump: loaded Not tainted 6.0.0-rc6+ #1
[ 4681.230999] NIP: c00000000068ee0c LR: c00000000068f2b8 CTR: 0000000000000000
[ 4681.238525] REGS: c000000006c0b560 TRAP: 0380 Not tainted (6.0.0-rc6+)
[ 4681.238532] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24028242 XER: 00000000
[ 4681.238556] CFAR: c00000000068edf4 IRQMASK: 0
[ 4681.238556] GPR00: c00000000068f2b8 c000000006c0b800 c000000002cf1700 c00c00000042f1c0
[ 4681.238556] GPR04: c000000006c0b860 0000000000000000 0000000000000002 0000000000000000
[ 4681.238556] GPR08: c000000002d404b0 0000000000000000 c00c00000042f1c0 0000000000000000
[ 4681.238556] GPR12: c0000000001cf080 c000000005100000 c000000000194298 c0000001fff9c480
[ 4681.238556] GPR16: c000000048cdb850 0000000000000007 0000000000000000 0000000000000000
[ 4681.238556] GPR20: 0000000000000001 c000000006c0b8f8 c00000000146b9d8 5deadbeef0000100
[ 4681.238556] GPR24: 5deadbeef0000122 c000000048cdb800 c000000006c0bc00 c000000006c0b8e8
[ 4681.238556] GPR28: c000000006c0b860 c00c00000042f1c0 0000000000000009 0000000000000009
[ 4681.238634] NIP [c00000000068ee0c] drop_buffers.constprop.0+0x4c/0x1c0
[ 4681.238643] LR [c00000000068f2b8] try_to_free_buffers+0x128/0x150
[ 4681.238650] Call Trace:
[ 4681.238654] [c000000006c0b800] [c000000006c0b880] 0xc000000006c0b880 (unreliable)
[ 4681.238663] [c000000006c0b840] [c000000006c0bc00] 0xc000000006c0bc00
[ 4681.238670] [c000000006c0b890] [c000000000498708] filemap_release_folio+0x88/0xb0
[ 4681.238679] [c000000006c0b8b0] [c0000000004c51c0] shrink_active_list+0x490/0x750
[ 4681.238688] [c000000006c0b9b0] [c0000000004c9f88] shrink_lruvec+0x3f8/0x430
[ 4681.238697] [c000000006c0baa0] [c0000000004ca1f4] shrink_node_memcgs+0x234/0x290
[ 4681.238704] [c000000006c0bb10] [c0000000004ca3c4] shrink_node+0x174/0x6b0
[ 4681.238711] [c000000006c0bbc0] [c0000000004cacf0] balance_pgdat+0x3f0/0x970
[ 4681.238718] [c000000006c0bd20] [c0000000004cb440] kswapd+0x1d0/0x450
[ 4681.238726] [c000000006c0bdc0] [c0000000001943d8] kthread+0x148/0x150
[ 4681.238735] [c000000006c0be10] [c00000000000cbe4] ret_from_kernel_thread+0x5c/0x64
[ 4681.238745] Instruction dump:
[ 4681.238749] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
[ 4681.238765] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
[ 4681.238782] ---[ end trace 0000000000000000 ]---
[ 4681.270607]
[ 4681.337460] Kernel attempted to read user page (6a) - exploit attempt? (uid: 0)
[ 4681.337469] BUG: Kernel NULL pointer dereference on read at 0x0000006a
[ 4681.337474] Faulting instruction address: 0xc00000000068ee0c
[ 4681.337478] Oops: Kernel access of bad area, sig: 11 [#2]
[ 4681.337481] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[ 4681.337486] Modules linked in: dm_flakey ext2 dm_snapshot dm_bufio dm_zero dm_mod loop ext4 mbcache jbd2 bonding rfkill tls sunrpc pseries_rng drm fuse drm_panel_orientation_quirks xfs libcrc32c sd_mod t10_pi sg ibmvscsi ibmveth scsi_transport_srp vmx_crypto
[ 4681.337517] CPU: 2 PID: 704157 Comm: xfs_io Kdump: loaded Tainted: G D 6.0.0-rc6+ #1
[ 4681.337523] NIP: c00000000068ee0c LR: c00000000068f2b8 CTR: 0000000000000000
[ 4681.337527] REGS: c000000036006ef0 TRAP: 0300 Tainted: G D (6.0.0-rc6+)
[ 4681.337532] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 28428242 XER: 00000001
[ 4681.337546] CFAR: c00000000000c80c DAR: 000000000000006a DSISR: 40000000 IRQMASK: 0
[ 4681.337546] GPR00: c00000000068f2b8 c000000036007190 c000000002cf1700 c00c000000424740
[ 4681.337546] GPR04: c0000000360071f0 0000000000000000 0000000000000002 0000000000000000
[ 4681.337546] GPR08: c000000002d404b0 0000000000000000 c00c000000424740 0000000000000002
[ 4681.337546] GPR12: 0000000000000000 c00000000ffce400 0000000000000000 c0000001fff9c480
[ 4681.337546] GPR16: c00000004960e050 0000000000000007 0000000000000000 0000000000000000
[ 4681.337546] GPR20: 0000000000000001 c000000036007288 c00000000146b9d8 5deadbeef0000100
[ 4681.337546] GPR24: 5deadbeef0000122 c00000004960e000 c000000036007678 c000000036007278
[ 4681.337546] GPR28: c0000000360071f0 c00c000000424740 000000000000000a 000000000000000a
[ 4681.337602] NIP [c00000000068ee0c] drop_buffers.constprop.0+0x4c/0x1c0
[ 4681.337608] LR [c00000000068f2b8] try_to_free_buffers+0x128/0x150
[ 4681.337613] Call Trace:
[ 4681.337616] [c000000036007190] [c000000036007210] 0xc000000036007210 (unreliable)
[ 4681.337622] [c0000000360071d0] [c000000036007678] 0xc000000036007678
[ 4681.337627] [c000000036007220] [c000000000498708] filemap_release_folio+0x88/0xb0
[ 4681.337633] [c000000036007240] [c0000000004c51c0] shrink_active_list+0x490/0x750
[ 4681.337640] [c000000036007340] [c0000000004c9f88] shrink_lruvec+0x3f8/0x430
[ 4681.337645] [c000000036007430] [c0000000004ca1f4] shrink_node_memcgs+0x234/0x290
[ 4681.337651] [c0000000360074a0] [c0000000004ca3c4] shrink_node+0x174/0x6b0
[ 4681.337656] [c000000036007550] [c0000000004cbd34] shrink_zones.constprop.0+0xd4/0x3e0
[ 4681.337661] [c0000000360075d0] [c0000000004cc158] do_try_to_free_pages+0x118/0x470
[ 4681.337667] [c000000036007650] [c0000000004cd084] try_to_free_pages+0x194/0x4c0
[ 4681.337673] [c000000036007720] [c00000000054cca4] __alloc_pages_slowpath.constprop.0+0x4f4/0xd80
[ 4681.337680] [c000000036007880] [c00000000054d95c] __alloc_pages+0x42c/0x580
[ 4681.337686] [c000000036007910] [c000000000587d88] alloc_pages+0xd8/0x1d0
[ 4681.337692] [c000000036007960] [c000000000587eb4] folio_alloc+0x34/0x90
[ 4681.337698] [c000000036007990] [c000000000498bc0] filemap_alloc_folio+0x40/0x60
[ 4681.337703] [c0000000360079b0] [c0000000004a0f54] __filemap_get_folio+0x224/0x790
[ 4681.337709] [c000000036007ab0] [c0000000004b4830] pagecache_get_page+0x30/0xb0
[ 4681.337715] [c000000036007ae0] [c008000003a9e4dc] ext4_da_write_begin+0x1a4/0x4f0 [ext4]
[ 4681.337742] [c000000036007b70] [c000000000498e54] generic_perform_write+0xf4/0x2b0
[ 4681.337748] [c000000036007c20] [c008000003a7d190] ext4_buffered_write_iter+0xa8/0x1a0 [ext4]
[ 4681.337770] [c000000036007c70] [c000000000615fc8] vfs_write+0x358/0x4b0
[ 4681.337776] [c000000036007d40] [c0000000006161f4] sys_pwrite64+0xd4/0x120
[ 4681.337782] [c000000036007da0] [c0000000000318d0] system_call_exception+0x180/0x430
[ 4681.337788] [c000000036007e10] [c00000000000be68] system_call_vectored_common+0xe8/0x278
[ 4681.337795] --- interrupt: 3000 at 0x7fff95651da4
[ 4681.337799] NIP: 00007fff95651da4 LR: 0000000000000000 CTR: 0000000000000000
[ 4681.337803] REGS: c000000036007e80 TRAP: 3000 Tainted: G D (6.0.0-rc6+)
[ 4681.337807] MSR: 800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 48082402 XER: 00000000
[ 4681.337822] IRQMASK: 0
[ 4681.337822] GPR00: 00000000000000b4 00007ffffaa52530 00007fff95767200 0000000000000003
[ 4681.337822] GPR04: 0000010031ac0000 0000000000010000 0000000000490000 00007fff9581a5a0
[ 4681.337822] GPR08: 00007fff95812e68 0000000000000000 0000000000000000 0000000000000000
[ 4681.337822] GPR12: 0000000000000000 00007fff9581a5a0 0000000000a00000 ffffffffffffffff
[ 4681.337822] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[ 4681.337822] GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000490000
[ 4681.337822] GPR24: 0000000000000049 0000000000000000 0000000000000000 0000000000010000
[ 4681.337822] GPR28: 0000010031ac0000 0000000000000003 0000000000000000 0000000000490000
[ 4681.337875] NIP [00007fff95651da4] 0x7fff95651da4
[ 4681.337878] LR [0000000000000000] 0x0
[ 4681.337881] --- interrupt: 3000
[ 4681.337884] Instruction dump:
[ 4681.337887] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
[ 4681.337897] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
[ 4681.337908] ---[ end trace 0000000000000000 ]---
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0
2022-09-27 1:17 [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0 Zorro Lang
@ 2022-09-29 21:28 ` Matthew Wilcox
2022-09-30 2:01 ` Michael Ellerman
0 siblings, 1 reply; 5+ messages in thread
From: Matthew Wilcox @ 2022-09-29 21:28 UTC (permalink / raw)
To: Zorro Lang; +Cc: linux-mm, linuxppc-dev, linux-ext4
On Tue, Sep 27, 2022 at 09:17:20AM +0800, Zorro Lang wrote:
> Hi mm and ppc list,
>
> Recently I started to hit a kernel panic [2] rarely on *ppc64le* with *1k
> blocksize* ext4. It's not easy to reproduce, but still has chance to trigger
> by loop running generic/048 on ppc64le (not sure all kind of ppc64le can
> reproduce it).
>
> Although I've reported a bug to ext4 [1] (more details refer to [1]), but I only
> hit it on ppc64le until now, and I'm not sure if it's an ext4 related bug, more
> likes folio related issue, so I cc mm and ppc mail list, hope to get more
> reviewing.
Argh. This is the wrong way to do it. Please stop using bugzilla.
Now there's discussion in two places and there's nowhere to see all
of it.
> [ 4681.230907] BUG: Kernel NULL pointer dereference at 0x00000069
> [ 4681.230922] Faulting instruction address: 0xc00000000068ee0c
> [ 4681.230929] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 4681.230934] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> [ 4681.230991] CPU: 0 PID: 82 Comm: kswapd0 Kdump: loaded Not tainted 6.0.0-rc6+ #1
> [ 4681.230999] NIP: c00000000068ee0c LR: c00000000068f2b8 CTR: 0000000000000000
> [ 4681.238525] REGS: c000000006c0b560 TRAP: 0380 Not tainted (6.0.0-rc6+)
> [ 4681.238532] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24028242 XER: 00000000
> [ 4681.238556] CFAR: c00000000068edf4 IRQMASK: 0
> [ 4681.238556] GPR00: c00000000068f2b8 c000000006c0b800 c000000002cf1700 c00c00000042f1c0
> [ 4681.238556] GPR04: c000000006c0b860 0000000000000000 0000000000000002 0000000000000000
> [ 4681.238556] GPR08: c000000002d404b0 0000000000000000 c00c00000042f1c0 0000000000000000
> [ 4681.238556] GPR12: c0000000001cf080 c000000005100000 c000000000194298 c0000001fff9c480
> [ 4681.238556] GPR16: c000000048cdb850 0000000000000007 0000000000000000 0000000000000000
> [ 4681.238556] GPR20: 0000000000000001 c000000006c0b8f8 c00000000146b9d8 5deadbeef0000100
> [ 4681.238556] GPR24: 5deadbeef0000122 c000000048cdb800 c000000006c0bc00 c000000006c0b8e8
> [ 4681.238556] GPR28: c000000006c0b860 c00c00000042f1c0 0000000000000009 0000000000000009
> [ 4681.238634] NIP [c00000000068ee0c] drop_buffers.constprop.0+0x4c/0x1c0
> [ 4681.238643] LR [c00000000068f2b8] try_to_free_buffers+0x128/0x150
> [ 4681.238650] Call Trace:
> [ 4681.238654] [c000000006c0b800] [c000000006c0b880] 0xc000000006c0b880 (unreliable)
> [ 4681.238663] [c000000006c0b840] [c000000006c0bc00] 0xc000000006c0bc00
> [ 4681.238670] [c000000006c0b890] [c000000000498708] filemap_release_folio+0x88/0xb0
> [ 4681.238679] [c000000006c0b8b0] [c0000000004c51c0] shrink_active_list+0x490/0x750
> [ 4681.238688] [c000000006c0b9b0] [c0000000004c9f88] shrink_lruvec+0x3f8/0x430
> [ 4681.238697] [c000000006c0baa0] [c0000000004ca1f4] shrink_node_memcgs+0x234/0x290
> [ 4681.238704] [c000000006c0bb10] [c0000000004ca3c4] shrink_node+0x174/0x6b0
> [ 4681.238711] [c000000006c0bbc0] [c0000000004cacf0] balance_pgdat+0x3f0/0x970
> [ 4681.238718] [c000000006c0bd20] [c0000000004cb440] kswapd+0x1d0/0x450
> [ 4681.238726] [c000000006c0bdc0] [c0000000001943d8] kthread+0x148/0x150
> [ 4681.238735] [c000000006c0be10] [c00000000000cbe4] ret_from_kernel_thread+0x5c/0x64
> [ 4681.238745] Instruction dump:
> [ 4681.238749] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
> [ 4681.238765] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
Running that through scripts/decodecode (with some minor hacks .. how
do PPC people do this properly?) I get:
0: fb c1 ff f0 std r30,-16(r1)
4: f8 21 ff c1 stdu r1,-64(r1)
8: 7c 7d 1b 78 mr r29,r3
c: 7c 9c 23 78 mr r28,r4
10: eb c3 00 28 ld r30,40(r3)
14: 7f df f3 78 mr r31,r30
18: 48 00 00 18 b 0x30
1c: 60 00 00 00 nop
20: 60 00 00 00 nop
24: eb ff 00 08 ld r31,8(r31)
28: 7c 3e f8 40 cmpld r30,r31
2c: 41 82 00 48 beq 0x74
30:* 81 5f 00 60 lwz r10,96(r31) <-- trapping instruction
34: e9 3f 00 00 ld r9,0(r31)
38: 55 29 07 7c rlwinm r9,r9,0,29,30
3c: 7d 29 53 78 or r9,r9,r10
That would seem to track; 96 is 0x60 and r31 contains 0x00..09, giving
us an effective address of 0x69.
It would be nice to know what source line that corresponds to. Could
you use scripts/faddr2line to turn drop_buffers.constprop.0+0x4c/0x1c0
into a line number? I can't because it needs the vmlinux you generated.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0
2022-09-29 21:28 ` Matthew Wilcox
@ 2022-09-30 2:01 ` Michael Ellerman
2022-09-30 18:59 ` Matthew Wilcox
0 siblings, 1 reply; 5+ messages in thread
From: Michael Ellerman @ 2022-09-30 2:01 UTC (permalink / raw)
To: Matthew Wilcox, Zorro Lang; +Cc: linux-mm, linux-ext4, linuxppc-dev
Matthew Wilcox <willy@infradead.org> writes:
> On Tue, Sep 27, 2022 at 09:17:20AM +0800, Zorro Lang wrote:
>> Hi mm and ppc list,
>>
>> Recently I started to hit a kernel panic [2] rarely on *ppc64le* with *1k
>> blocksize* ext4. It's not easy to reproduce, but still has chance to trigger
>> by loop running generic/048 on ppc64le (not sure all kind of ppc64le can
>> reproduce it).
>>
>> Although I've reported a bug to ext4 [1] (more details refer to [1]), but I only
>> hit it on ppc64le until now, and I'm not sure if it's an ext4 related bug, more
>> likes folio related issue, so I cc mm and ppc mail list, hope to get more
>> reviewing.
>
> Argh. This is the wrong way to do it. Please stop using bugzilla.
> Now there's discussion in two places and there's nowhere to see all
> of it.
>
>> [ 4681.230907] BUG: Kernel NULL pointer dereference at 0x00000069
>> [ 4681.230922] Faulting instruction address: 0xc00000000068ee0c
>> [ 4681.230929] Oops: Kernel access of bad area, sig: 11 [#1]
>> [ 4681.230934] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>> [ 4681.230991] CPU: 0 PID: 82 Comm: kswapd0 Kdump: loaded Not tainted 6.0.0-rc6+ #1
>> [ 4681.230999] NIP: c00000000068ee0c LR: c00000000068f2b8 CTR: 0000000000000000
>> [ 4681.238525] REGS: c000000006c0b560 TRAP: 0380 Not tainted (6.0.0-rc6+)
>> [ 4681.238532] MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24028242 XER: 00000000
>> [ 4681.238556] CFAR: c00000000068edf4 IRQMASK: 0
>> [ 4681.238556] GPR00: c00000000068f2b8 c000000006c0b800 c000000002cf1700 c00c00000042f1c0
>> [ 4681.238556] GPR04: c000000006c0b860 0000000000000000 0000000000000002 0000000000000000
>> [ 4681.238556] GPR08: c000000002d404b0 0000000000000000 c00c00000042f1c0 0000000000000000
>> [ 4681.238556] GPR12: c0000000001cf080 c000000005100000 c000000000194298 c0000001fff9c480
>> [ 4681.238556] GPR16: c000000048cdb850 0000000000000007 0000000000000000 0000000000000000
>> [ 4681.238556] GPR20: 0000000000000001 c000000006c0b8f8 c00000000146b9d8 5deadbeef0000100
>> [ 4681.238556] GPR24: 5deadbeef0000122 c000000048cdb800 c000000006c0bc00 c000000006c0b8e8
>> [ 4681.238556] GPR28: c000000006c0b860 c00c00000042f1c0 0000000000000009 0000000000000009
>> [ 4681.238634] NIP [c00000000068ee0c] drop_buffers.constprop.0+0x4c/0x1c0
>> [ 4681.238643] LR [c00000000068f2b8] try_to_free_buffers+0x128/0x150
>> [ 4681.238650] Call Trace:
>> [ 4681.238654] [c000000006c0b800] [c000000006c0b880] 0xc000000006c0b880 (unreliable)
>> [ 4681.238663] [c000000006c0b840] [c000000006c0bc00] 0xc000000006c0bc00
>> [ 4681.238670] [c000000006c0b890] [c000000000498708] filemap_release_folio+0x88/0xb0
>> [ 4681.238679] [c000000006c0b8b0] [c0000000004c51c0] shrink_active_list+0x490/0x750
>> [ 4681.238688] [c000000006c0b9b0] [c0000000004c9f88] shrink_lruvec+0x3f8/0x430
>> [ 4681.238697] [c000000006c0baa0] [c0000000004ca1f4] shrink_node_memcgs+0x234/0x290
>> [ 4681.238704] [c000000006c0bb10] [c0000000004ca3c4] shrink_node+0x174/0x6b0
>> [ 4681.238711] [c000000006c0bbc0] [c0000000004cacf0] balance_pgdat+0x3f0/0x970
>> [ 4681.238718] [c000000006c0bd20] [c0000000004cb440] kswapd+0x1d0/0x450
>> [ 4681.238726] [c000000006c0bdc0] [c0000000001943d8] kthread+0x148/0x150
>> [ 4681.238735] [c000000006c0be10] [c00000000000cbe4] ret_from_kernel_thread+0x5c/0x64
>> [ 4681.238745] Instruction dump:
>> [ 4681.238749] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
>> [ 4681.238765] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
>
> Running that through scripts/decodecode (with some minor hacks .. how
> do PPC people do this properly?)
We've just always used our own scripts. Mine is here: https://github.com/mpe/misc-scripts/blob/master/ppc/ppc-disasm
I've added an issue to our tracker for us to get scripts/decodecode
working on our oopses (eventually).
> I get:
>
> 0: fb c1 ff f0 std r30,-16(r1)
> 4: f8 21 ff c1 stdu r1,-64(r1)
> 8: 7c 7d 1b 78 mr r29,r3
> c: 7c 9c 23 78 mr r28,r4
> 10: eb c3 00 28 ld r30,40(r3)
> 14: 7f df f3 78 mr r31,r30
> 18: 48 00 00 18 b 0x30
> 1c: 60 00 00 00 nop
> 20: 60 00 00 00 nop
> 24: eb ff 00 08 ld r31,8(r31)
> 28: 7c 3e f8 40 cmpld r30,r31
> 2c: 41 82 00 48 beq 0x74
> 30:* 81 5f 00 60 lwz r10,96(r31) <-- trapping instruction
> 34: e9 3f 00 00 ld r9,0(r31)
> 38: 55 29 07 7c rlwinm r9,r9,0,29,30
> 3c: 7d 29 53 78 or r9,r9,r10
>
> That would seem to track; 96 is 0x60 and r31 contains 0x00..09, giving
> us an effective address of 0x69.
>
> It would be nice to know what source line that corresponds to. Could
> you use scripts/faddr2line to turn drop_buffers.constprop.0+0x4c/0x1c0
> into a line number? I can't because it needs the vmlinux you generated.
You'll need: https://lore.kernel.org/all/20220927075211.897152-1-srikar@linux.vnet.ibm.com/
I don't have the same vmlinux obviously, but mine seems to match up
pretty closely, I get:
c0000000004e3900 <drop_buffers.constprop.0>:
c0000000004e3900: b9 00 4c 3c addis r2,r12,185
c0000000004e3904: 00 c5 42 38 addi r2,r2,-15104
c0000000004e3908: a6 02 08 7c mflr r0
c0000000004e390c: 29 4f b8 4b bl c000000000068834 <_mcount> # ^ entry & ftrace stuff
c0000000004e3910: e0 ff 81 fb std r28,-32(r1)
c0000000004e3914: e8 ff a1 fb std r29,-24(r1)
c0000000004e3918: 78 23 9c 7c mr r28,r4
c0000000004e391c: 78 1b 7d 7c mr r29,r3
c0000000004e3920: f8 ff e1 fb std r31,-8(r1)
c0000000004e3924: f0 ff c1 fb std r30,-16(r1)
c0000000004e3928: c1 ff 21 f8 stdu r1,-64(r1) # ^ save regs and create stack frame
c0000000004e392c: 28 00 c3 eb ld r30,40(r3) # r30 = folio->private (0000000000000009)
c0000000004e3930: 78 f3 df 7f mr r31,r30 # r31 = folio->private = head = bh
c0000000004e3934: 18 00 00 48 b c0000000004e394c <drop_buffers.constprop.0+0x4c> ->
c0000000004e3938: 00 00 00 60 nop
c0000000004e393c: 00 00 42 60 ori r2,r2,0
c0000000004e3940: 08 00 ff eb ld r31,8(r31)
c0000000004e3944: 40 f8 3e 7c cmpld r30,r31
c0000000004e3948: 48 00 82 41 beq c0000000004e3990 <drop_buffers.constprop.0+0x90>
c0000000004e394c: 60 00 5f 81 lwz r10,96(r31) # r10 = bh->b_count
$ ./scripts/faddr2line .build/vmlinux drop_buffers.constprop.0+0x4c
drop_buffers.constprop.0+0x4c/0x170:
arch_atomic_read at arch/powerpc/include/asm/atomic.h:30
(inlined by) atomic_read at include/linux/atomic/atomic-instrumented.h:28
(inlined by) buffer_busy at fs/buffer.c:2859
(inlined by) drop_buffers at fs/buffer.c:2871
static inline int buffer_busy(struct buffer_head *bh)
{
return atomic_read(&bh->b_count) |
(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}
struct folio {
union {
struct {
long unsigned int flags; /* 0 8 */
union {
struct list_head lru; /* 8 16 */
struct {
void * __filler; /* 8 8 */
unsigned int mlock_count; /* 16 4 */
}; /* 8 16 */
}; /* 8 16 */
struct address_space * mapping; /* 24 8 */
long unsigned int index; /* 32 8 */
void * private; /* 40 8 */ <----
struct buffer_head {
long unsigned int b_state; /* 0 8 */
struct buffer_head * b_this_page; /* 8 8 */
struct page * b_page; /* 16 8 */
sector_t b_blocknr; /* 24 8 */
size_t b_size; /* 32 8 */
char * b_data; /* 40 8 */
struct block_device * b_bdev; /* 48 8 */
bh_end_io_t * b_end_io; /* 56 8 */
void * b_private; /* 64 8 */
struct list_head b_assoc_buffers; /* 72 16 */
struct address_space * b_assoc_map; /* 88 8 */
atomic_t b_count; /* 96 4 */ <----
The buffer_head comes from folio_buffers(folio):
static bool
drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
{
struct buffer_head *head = folio_buffers(folio);
Which is == folio_get_private()
r3 and r29 still hold folio = c00c00000042f1c0
That's a valid looking vmemmap address.
So we have a valid folio, but its private field == 9 ?
Seems like all sorts of things get stuffed into page->private, so
presumably 9 is not necessarily a corrupt value, just not what we're
expecting. But I'm out of my depth so over to you :)
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0
2022-09-30 2:01 ` Michael Ellerman
@ 2022-09-30 18:59 ` Matthew Wilcox
2022-10-05 11:13 ` Michael Ellerman
0 siblings, 1 reply; 5+ messages in thread
From: Matthew Wilcox @ 2022-09-30 18:59 UTC (permalink / raw)
To: Michael Ellerman; +Cc: Zorro Lang, linux-mm, linux-ext4, linuxppc-dev
On Fri, Sep 30, 2022 at 12:01:26PM +1000, Michael Ellerman wrote:
> Matthew Wilcox <willy@infradead.org> writes:
> >> [ 4681.238745] Instruction dump:
> >> [ 4681.238749] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
> >> [ 4681.238765] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
> >
> > Running that through scripts/decodecode (with some minor hacks .. how
> > do PPC people do this properly?)
>
> We've just always used our own scripts. Mine is here: https://github.com/mpe/misc-scripts/blob/master/ppc/ppc-disasm
>
> I've added an issue to our tracker for us to get scripts/decodecode
> working on our oopses (eventually).
Would you be open to changing your oops printer to do
s/Instruction dump/Code/ ? That would make it work without any other
changes.
$ CROSS_COMPILE=powerpc-linux-gnu- ./scripts/decodecode
Code:
fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
^D
gives the right answer. You could also do like x86 and put Code: on
the same line as the first set of hex (not that it matters; the parser
is fairly flexible). This would also work ...
diff --git a/scripts/decodecode b/scripts/decodecode
index c711a196511c..0cadf1a37cbf 100755
--- a/scripts/decodecode
+++ b/scripts/decodecode
@@ -27,8 +27,8 @@ cont=
while read i ; do
case "$i" in
-*Code:*)
- code=$i
+*Code:* | *'Instruction dump':*)
+ code=${i##*:}
cont=yes
;;
*)
@@ -51,7 +51,7 @@ if [ -z "$code" ]; then
fi
echo $code
-code=`echo $code | sed -e 's/.*Code: //'`
+code=`echo $code`
width=`expr index "$code" ' '`
width=$((($width-1)/2))
(no, i don't know why i need that echo $code line; trimming trailing
spaces, maybe? shell is a terrible language)
> $ ./scripts/faddr2line .build/vmlinux drop_buffers.constprop.0+0x4c
> drop_buffers.constprop.0+0x4c/0x170:
> arch_atomic_read at arch/powerpc/include/asm/atomic.h:30
> (inlined by) atomic_read at include/linux/atomic/atomic-instrumented.h:28
> (inlined by) buffer_busy at fs/buffer.c:2859
> (inlined by) drop_buffers at fs/buffer.c:2871
>
> static inline int buffer_busy(struct buffer_head *bh)
> {
> return atomic_read(&bh->b_count) |
> (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
> }
>
> struct folio {
> union {
> struct {
> long unsigned int flags; /* 0 8 */
> union {
> struct list_head lru; /* 8 16 */
> struct {
> void * __filler; /* 8 8 */
> unsigned int mlock_count; /* 16 4 */
> }; /* 8 16 */
> }; /* 8 16 */
> struct address_space * mapping; /* 24 8 */
> long unsigned int index; /* 32 8 */
> void * private; /* 40 8 */ <----
>
> struct buffer_head {
> long unsigned int b_state; /* 0 8 */
> struct buffer_head * b_this_page; /* 8 8 */
> struct page * b_page; /* 16 8 */
> sector_t b_blocknr; /* 24 8 */
> size_t b_size; /* 32 8 */
> char * b_data; /* 40 8 */
> struct block_device * b_bdev; /* 48 8 */
> bh_end_io_t * b_end_io; /* 56 8 */
> void * b_private; /* 64 8 */
> struct list_head b_assoc_buffers; /* 72 16 */
> struct address_space * b_assoc_map; /* 88 8 */
> atomic_t b_count; /* 96 4 */ <----
>
> The buffer_head comes from folio_buffers(folio):
>
> static bool
> drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
> {
> struct buffer_head *head = folio_buffers(folio);
>
> Which is == folio_get_private()
>
> r3 and r29 still hold folio = c00c00000042f1c0
>
> That's a valid looking vmemmap address.
>
> So we have a valid folio, but its private field == 9 ?
>
> Seems like all sorts of things get stuffed into page->private, so
> presumably 9 is not necessarily a corrupt value, just not what we're
> expecting. But I'm out of my depth so over to you :)
Yes, all kinds of things do get stuffed into folio->private, alas.
However, for an ext4 folio, it should either be NULL or a pointer to
a buffer_head. It'd be interesting to insert ...
if ((long)head < 4096) dump_page(&folio->page, "bad bh");
in drop_buffers() before we actually dereference the 'head'.
My suspicion is that page->private and PagePrivate have got out of sync
somehow; we're trying to reclaim the PG_private bit and there have been
some similar problems of this type in the past.
I had success debugging this kind of problem with this patch:
commit 80eba374eab3
Author: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Tue Jun 21 07:04:32 2022 -0400
mm: Add an assertion that PG_private and folio->private are in sync
We are trying to eliminate the use of the PG_private flag. To do so,
it must be in sync with the use of the ->private field. It usually
is, and this assert should catch any cases where it isn't.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index 15800334147b..2f26c32ea1cd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1529,6 +1529,9 @@ void folio_unlock(struct folio *folio)
BUILD_BUG_ON(PG_waiters != 7);
BUILD_BUG_ON(PG_locked > 7);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+ VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio) &&
+ (folio_test_private(folio) ==
+ !folio_get_private(folio)), folio);
if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
folio_wake_bit(folio, PG_locked);
}
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0
2022-09-30 18:59 ` Matthew Wilcox
@ 2022-10-05 11:13 ` Michael Ellerman
0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2022-10-05 11:13 UTC (permalink / raw)
To: Matthew Wilcox; +Cc: Zorro Lang, linux-mm, linux-ext4, linuxppc-dev
Matthew Wilcox <willy@infradead.org> writes:
> On Fri, Sep 30, 2022 at 12:01:26PM +1000, Michael Ellerman wrote:
>> Matthew Wilcox <willy@infradead.org> writes:
>> >> [ 4681.238745] Instruction dump:
>> >> [ 4681.238749] fbc1fff0 f821ffc1 7c7d1b78 7c9c2378 ebc30028 7fdff378 48000018 60000000
>> >> [ 4681.238765] 60000000 ebff0008 7c3ef840 41820048 <815f0060> e93f0000 5529077c 7d295378
>> >
>> > Running that through scripts/decodecode (with some minor hacks .. how
>> > do PPC people do this properly?)
>>
>> We've just always used our own scripts. Mine is here: https://github.com/mpe/misc-scripts/blob/master/ppc/ppc-disasm
>>
>> I've added an issue to our tracker for us to get scripts/decodecode
>> working on our oopses (eventually).
>
> Would you be open to changing your oops printer to do
> s/Instruction dump/Code/ ? That would make it work without any other
> changes.
Yeah, we're the only arch that uses "Instruction dump".
For userspace instructions we already print "code".
I'll send a patch switching to "Code:".
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-10-05 11:13 UTC | newest]
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2022-09-27 1:17 [Bug report] BUG: Kernel NULL pointer dereference at 0x00000069, filemap_release_folio+0x88/0xb0 Zorro Lang
2022-09-29 21:28 ` Matthew Wilcox
2022-09-30 2:01 ` Michael Ellerman
2022-09-30 18:59 ` Matthew Wilcox
2022-10-05 11:13 ` Michael Ellerman
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