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Date: Tue, 10 Oct 2017 21:31:06 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: kernel test robot <xiaolong.ye@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Brian Gerst <brgerst@...il.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Jiri Slaby <jslaby@...e.cz>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Mike Galbraith <efault@....de>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>, lkp@...org,
linux-mm@...ck.org
Subject: Re: [lkp-robot] [x86/kconfig] 81d3871900:
BUG:unable_to_handle_kernel
On Tue, Oct 10, 2017 at 08:15:13PM +0800, kernel test robot wrote:
>
> FYI, we noticed the following commit (built with gcc-4.8):
>
> commit: 81d387190039c14edac8de2b3ec789beb899afd9 ("x86/kconfig: Consolidate unwinders into multiple choice selection")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> in testcase: boot
>
> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -m 512M
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
>
> +------------------------------------------+------------+------------+
> | | a34a766ff9 | 81d3871900 |
> +------------------------------------------+------------+------------+
> | boot_successes | 24 | 5 |
> | boot_failures | 12 | 31 |
> | BUG:kernel_hang_in_test_stage | 12 | 1 |
> | BUG:unable_to_handle_kernel | 0 | 30 |
> | Oops:#[##] | 0 | 30 |
> | Kernel_panic-not_syncing:Fatal_exception | 0 | 30 |
> +------------------------------------------+------------+------------+
>
>
>
> [ 5.324797] BUG: unable to handle kernel paging request at ffff88001c4b0000
> [ 5.326126] IP: slob_free+0x2bf/0x3d7
> [ 5.328023] PGD 17d9c067
> [ 5.328023] P4D 17d9c067
> [ 5.328023] PUD 17d9d067
> [ 5.328023] PMD 1f91e067
> [ 5.328023] PTE 800000001c4b0060
> [ 5.328023]
> [ 5.328023] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [ 5.328023] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.13.0-rc1-00044-g81d3871 #1
> [ 5.328023] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> [ 5.328023] task: ffff8800002fa000 task.stack: ffffc900000d0000
> [ 5.328023] RIP: 0010:slob_free+0x2bf/0x3d7
> [ 5.328023] RSP: 0000:ffffc900000d3d58 EFLAGS: 00010002
> [ 5.328023] RAX: 0000000000000027 RBX: ffff88001c4affb0 RCX: 0000000000000000
> [ 5.328023] RDX: ffff88001c4af000 RSI: 0000000000000000 RDI: ffff88001c4afffe
> [ 5.328023] RBP: ffff88001c4afffe R08: 0000000000000001 R09: 0000000000000000
> [ 5.328023] R10: ffffea000069a420 R11: ffff88001ffdb000 R12: ffff88001c4aff5c
> [ 5.328023] R13: 0000000000000027 R14: 0000000000000027 R15: 0000000000000027
> [ 5.328023] FS: 0000000000000000(0000) GS:ffff88001f600000(0000) knlGS:0000000000000000
> [ 5.328023] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 5.328023] CR2: ffff88001c4b0000 CR3: 0000000016211000 CR4: 00000000000406b0
> [ 5.328023] Call Trace:
> [ 5.328023] ? link_target+0xb2/0xc7
> [ 5.328023] kfree+0x158/0x1b6
> [ 5.328023] link_target+0xb2/0xc7
> [ 5.328023] new_node+0x32b/0x4d1
> [ 5.328023] gcov_event+0x33e/0x546
> [ 5.328023] ? gcov_persist_setup+0xbb/0xbb
> [ 5.328023] gcov_enable_events+0x3c/0x89
> [ 5.328023] gcov_fs_init+0x134/0x191
> [ 5.328023] do_one_initcall+0x10e/0x2df
> [ 5.328023] kernel_init_freeable+0x3ec/0x559
> [ 5.328023] ? rest_init+0x145/0x145
> [ 5.328023] kernel_init+0xc/0x1a8
> [ 5.328023] ret_from_fork+0x2a/0x40
> [ 5.328023] Code: e8 8d f7 ff ff 48 ff 05 c9 8c 91 02 85 c0 75 51 49 0f bf c5 48 ff 05 c2 8c 91 02 48 8d 3c 43 48 39 ef 75 3d 48 ff 05 ba 8c 91 02 <8b> 6d 00 66 85 ed 7e 09 48 ff 05 b3 8c 91 02 eb 05 bd 01 00 00
> [ 5.328023] RIP: slob_free+0x2bf/0x3d7 RSP: ffffc900000d3d58
> [ 5.328023] CR2: ffff88001c4b0000
> [ 5.328023] ---[ end trace f8ee1579929b04f0 ]---
Adding the slub maintainers. Is slob still supposed to work?
The bisection is blaming the ORC unwinder, but I'm having trouble
finding anything ORC specific about it. I wonder if the disabling of
frame pointers changed the code generation enough to trigger this bug
somehow.
Looking at the panic, the code in slob_free() was:
0: e8 8d f7 ff ff callq 0xfffffffffffff792
5: 48 ff 05 c9 8c 91 02 incq 0x2918cc9(%rip) # 0x2918cd5
c: 85 c0 test %eax,%eax
e: 75 51 jne 0x61
10: 49 0f bf c5 movswq %r13w,%rax
14: 48 ff 05 c2 8c 91 02 incq 0x2918cc2(%rip) # 0x2918cdd
1b: 48 8d 3c 43 lea (%rbx,%rax,2),%rdi
1f: 48 39 ef cmp %rbp,%rdi
22: 75 3d jne 0x61
24: 48 ff 05 ba 8c 91 02 incq 0x2918cba(%rip) # 0x2918ce5
2b:* 8b 6d 00 mov 0x0(%rbp),%ebp <-- trapping instruction
2e: 66 85 ed test %bp,%bp
31: 7e 09 jle 0x3c
33: 48 ff 05 b3 8c 91 02 incq 0x2918cb3(%rip) # 0x2918ced
3a: eb 05 jmp 0x41
3c: bd .byte 0xbd
3d: 01 00 add %eax,(%rax)
The slob_free() code tried to read four bytes at ffff88001c4afffe, and
ended up reading past the page into a bad area. I think the bad address
(ffff88001c4afffe) was returned from slob_next() and it panicked trying
to read s->units in slob_units().
Interestingly, I've found that I get panics when booting with
CONFIG_SLOB enabled, with both ORC and frame pointers:
general protection fault: 0000 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 58 Comm: kworker/0:1 Not tainted 4.13.0-rc1+ #74
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014
Workqueue: crypto mcryptd_flusher
task: ffff880139a98000 task.stack: ffffc9000082c000
RIP: 0010:skip_7+0x0/0x67
RSP: 0000:ffffc9000082fd88 EFLAGS: 00010246
RAX: ffff880134b65e34 RBX: 00000000f7654321 RCX: 0000000000000003
RDX: 0000000000000000 RSI: ffffffff81d22039 RDI: ffff880135be0248
RBP: ffffc9000082fd90 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8238d260
R13: ffff88013a7e53a8 R14: 00000000fffb7593 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff88013a600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000001e11000 CR4: 00000000001406f0
Call Trace:
sha256_ctx_mgr_flush+0x28/0x30
sha256_mb_flusher+0x53/0x120
mcryptd_flusher+0xc4/0xf0
process_one_work+0x253/0x6b0
worker_thread+0x4d/0x3b0
? preempt_count_sub+0x9b/0x100
kthread+0x12c/0x150
? process_one_work+0x6b0/0x6b0
? kthread_create_on_node+0x70/0x70
ret_from_fork+0x2a/0x40
Code: 89 87 30 01 00 00 c7 87 58 01 00 00 ff ff ff ff 48 83 bf a0 01 00 00 00 75 11 48 89 87 38 01 00 00 c7 87 5c 01 00 00 ff ff ff ff <c5> f9 6f 87 40 01 00 00 c5 f9 6f 8f 50 01 00 00 c4 e2 79 3b d1
RIP: skip_7+0x0/0x67 RSP: ffffc9000082fd88
I have no idea how that crypto panic could could be related to slob, but
at least it goes away when I switch to slub.
--
Josh
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