linux-kernel - Re: [mm, slab/slub] 7b39adbb1b: WARNING:at_mm/slab.h:#kmem_cache

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Message-ID: <d6e6b64c-2870-1fbb-bca2-a27732af1ec3@suse.cz>
Date:   Tue, 23 Jun 2020 13:35:21 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Kees Cook <keescook@...omium.org>,
        Roman Gushchin <guro@...com>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Garrett <mjg59@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Vijayanand Jitta <vjitta@...eaurora.org>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org
Subject: Re: [mm, slab/slub] 7b39adbb1b: WARNING:at_mm/slab.h:#kmem_cache_free

On 6/23/20 11:02 AM, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed the following commit (built with gcc-6):
> 
> commit: 7b39adbb1b1d3e73df9066a8d1e93a83c18d7730 ("mm, slab/slub: improve error reporting and overhead of cache_from_obj()")
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> 
> in testcase: boot
> 
> on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> 
> 
> +--------------------------------------------------------+------------+------------+
> |                                                        | 5a2a0a5f04 | 7b39adbb1b |
> +--------------------------------------------------------+------------+------------+
> | boot_successes                                         | 4          | 0          |
> | boot_failures                                          | 4          | 8          |
> | WARNING:at_kernel/trace/trace.c:#trace_find_next_entry | 4          | 4          |
> | EIP:trace_find_next_entry                              | 4          | 4          |
> | WARNING:at_mm/slab.h:#kmem_cache_free                  | 0          | 8          |
> | EIP:kmem_cache_free                                    | 0          | 8          |
> +--------------------------------------------------------+------------+------------+
> 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <rong.a.chen@...el.com>
> 
> 
> [    3.251054] WARNING: CPU: 0 PID: 8 at mm/slab.h:298 kmem_cache_free+0x5/0x170

So this is due to the latest fixups.

Roman suggested VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS)); which triggered here.
For Kees, the cache_from_obj() is again shared between SLAB and SLUB and is
testing kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS).

However under CONFIG_SLAB, SLAB_DEBUG_FLAGS doesn't include SLAB_CONSISTENCY_CHECKS.

I think I'll need to move the VM_WARN_ON_ONCE() under #ifdef CONFIG_SLUB ?

> [    3.251054] Modules linked in:
> [    3.251054] CPU: 0 PID: 8 Comm: kdevtmpfs Not tainted 5.8.0-rc1-00277-g7b39adbb1b1d3 #1
> [    3.251054] EIP: kmem_cache_free+0x5/0x170
> [    3.251054] Code: 9f 8c 89 f8 e8 cc 58 fd ff 0f 0b 8d 78 ff e9 77 ff ff ff e8 2d d3 90 00 8d b4 26 00 00 00 00 8d b6 00 00 00 00 66 66 66 66 90 <0f> 0b 85 c0 0f 84 a6 00 00 00 8b 0d 64 50 b7 8c 85 c9 0f 84 33 01
> [    3.251054] EAX: 80090780 EBX: 802b4000 ECX: 00000000 EDX: 802b4000
> [    3.251054] ESI: 802b4000 EDI: 80305e04 EBP: 80305df4 ESP: 80305dec
> [    3.251054] DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068 EFLAGS: 00010246
> [    3.251054] CR0: 80050033 CR2: ffffffff CR3: 0ceb2000 CR4: 000406b0
> [    3.251054] Call Trace:
> [    3.251054]  ? putname+0x5c/0x60
> [    3.251054]  filename_lookup+0xde/0x1a0
> [    3.251054]  ? rcu_read_lock_sched_held+0x20/0x50
> [    3.251054]  ? strncpy_from_user+0x21/0x1a0
> [    3.251054]  user_path_at_empty+0x2a/0x40
> [    3.251054]  do_mount+0x5d/0x9b0
> [    3.251054]  devtmpfsd+0x69/0x2c0
> [    3.251054]  ? sched_clock_cpu+0x44/0xc0
> [    3.251054]  ? _raw_spin_unlock_irqrestore+0x2a/0x72
> [    3.251054]  ? trace_hardirqs_on+0xbf/0x270
> [    3.251054]  ? __kthread_parkme+0x5a/0x80
> [    3.251054]  kthread+0xf0/0x120
> [    3.251054]  ? public_dev_mount+0x40/0x40
> [    3.251054]  ? kthread_create_worker_on_cpu+0x20/0x20
> [    3.251054]  ret_from_fork+0x19/0x30
> [    3.251054] irq event stamp: 41
> [    3.251054] hardirqs last  enabled at (41): [<8ba11885>] set_root+0x95/0x190
> [    3.251054] hardirqs last disabled at (40): [<8ba11856>] set_root+0x66/0x190
> [    3.251054] softirqs last  enabled at (0): [<8b87027b>] copy_process+0x3eb/0x15b0
> [    3.251054] softirqs last disabled at (0): [<00000000>] 0x0
> [    3.251054] ---[ end trace e72be312a52f9020 ]---
> 
> 
> To reproduce:
> 
>         # build kernel
> 	cd linux
> 	cp config-5.8.0-rc1-00277-g7b39adbb1b1d3 .config
> 	make HOSTCC=gcc-6 CC=gcc-6 ARCH=i386 olddefconfig prepare modules_prepare bzImage
> 
>         git clone https://github.com/intel/lkp-tests.git
>         cd lkp-tests
>         bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email
> 
> 
> 
> Thanks,
> Rong Chen
>