slub freelist issue / BUG: unable to handle page fault for address: 000000003ffe0018

Vegard Nossum
2020-06-04T17:14:55Z

Hi all,

I ran into a boot problem with latest linus/master
(6929f71e46bdddbf1c4d67c2728648176c67c555) that manifests like this:

hpet0: 3 comparators, 64-bit 100.000000 MHz counter
clocksource: Switched to clocksource tsc-early
BUG: unable to handle page fault for address: 000000003ffe0018
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0+ #211
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
RIP: 0010:kmem_cache_alloc+0x70/0x1d0
Code: 00 00 4c 8b 45 00 65 49 8b 50 08 65 4c 03 05 6f cc e7 7e 4d 8b 20
4d 85 e4 0f 84 3d 01 00 00 8b 45 20 48 8b 7d 00 48 8d 4a 01 <49> 8b 1c
04 4c 89 e0 65 48 0f c7 0f 0f 94 c0 84 c0 74 c5 8b 45 20
RSP: 0000:ffffc90000013df8 EFLAGS: 00010206
RAX: 0000000000000018 RBX: ffffffff81c49200 RCX: 0000000000000002
RDX: 0000000000000001 RSI: 0000000000000dc0 RDI: 000000000002b300
RBP: ffff88803e403d00 R08: ffff88803ec2b300 R09: 0000000000000001
R10: 0000000000000dc0 R11: 0000000000000006 R12: 000000003ffe0000
R13: ffffffff8110a583 R14: 0000000000000dc0 R15: ffffffff81c49a80
FS: 0000000000000000(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000003ffe0018 CR3: 0000000001c0a001 CR4: 00000000003606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__trace_define_field+0x33/0xa0
event_trace_init+0xeb/0x2b4
tracer_init_tracefs+0x60/0x195
? register_tracer+0x1e7/0x1e7
do_one_initcall+0x74/0x160
kernel_init_freeable+0x190/0x1f0
? rest_init+0x9a/0x9a
kernel_init+0x5/0xf6
ret_from_fork+0x35/0x40
CR2: 000000003ffe0018
---[ end trace 707efa023f2ee960 ]---
RIP: 0010:kmem_cache_alloc+0x70/0x1d0

Bisection gives me:

commit 3202fa62fb43087387c65bfa9c100feffac74aa6
Author: Kees Cook <keescook@chromium.org>
Date: Wed Apr 1 21:04:27 2020 -0700

slub: relocate freelist pointer to middle of object

Reverting these three commits fixes it:

3202fa62fb43087387c65bfa9c100feffac74aa6 slub: relocate freelist pointer
to middle of object
89b83f282d8ba380cf2124f88106c57df49c538c slub: avoid redzone when
choosing freepointer location
cbfc35a48609ceac978791e3ab9dde0c01f8cb20 mm/slub: fix incorrect
interpretation of s->offset

Vegard