linux-kernel - Re: [PATCH] mm/slub: fix to return errno if kmalloc() fails

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Message-ID: <6cfc1406-7239-69d0-42dc-a9d61c1ea54d@kernel.org>
Date:   Tue, 13 Sep 2022 11:27:36 +0800
From:   Chao Yu <chao@...nel.org>
To:     "Vlastimil Babka (SUSE)" <vbabka@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>
Cc:     Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, jaegeuk@...nel.org,
        Chao Yu <chao.yu@...o.com>, stable@...nel.org,
        syzbot+81684812ea68216e08c5@...kaller.appspotmail.com,
        David Rientjes <rientjes@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH] mm/slub: fix to return errno if kmalloc() fails

On 2022/9/9 5:25, Vlastimil Babka (SUSE) wrote:
> On 8/31/22 05:09, Muchun Song wrote:
>>
>>
>>> On Aug 30, 2022, at 22:10, Chao Yu <chao@...nel.org> wrote:
> 
> Please use scripts/get_maintainer.pl next time, I could have missed this.

Oh, my bad, will Cc all maintainers next time.

Thanks,

> 
>>> From: Chao Yu <chao.yu@...o.com>
>>>
>>> In create_unique_id(), kmalloc(, GFP_KERNEL) can fail due to
>>> out-of-memory, if it fails, return errno correctly rather than
>>> triggering panic via BUG_ON();
>>
>> I tend to agree with you. A mount operation shouldn’t panic the
>> kernel.
> 
> Hmm kmalloc(64) shouldn't normally due that due to the the underlying page
> allocation falling into the "too small to fail" category, wonder if
> syzkaller was doing anything special here?
> 
> But yeah we should get rid of all BUG_ONs eventually, just not sure if
> stable@ is needed here.
> 
>>>
>>> kernel BUG at mm/slub.c:5893!
>>> Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>>>
>>> Call trace:
>>> sysfs_slab_add+0x258/0x260 mm/slub.c:5973
>>> __kmem_cache_create+0x60/0x118 mm/slub.c:4899
>>> create_cache mm/slab_common.c:229 [inline]
>>> kmem_cache_create_usercopy+0x19c/0x31c mm/slab_common.c:335
>>> kmem_cache_create+0x1c/0x28 mm/slab_common.c:390
>>> f2fs_kmem_cache_create fs/f2fs/f2fs.h:2766 [inline]
>>> f2fs_init_xattr_caches+0x78/0xb4 fs/f2fs/xattr.c:808
>>> f2fs_fill_super+0x1050/0x1e0c fs/f2fs/super.c:4149
>>> mount_bdev+0x1b8/0x210 fs/super.c:1400
>>> f2fs_mount+0x44/0x58 fs/f2fs/super.c:4512
>>> legacy_get_tree+0x30/0x74 fs/fs_context.c:610
>>> vfs_get_tree+0x40/0x140 fs/super.c:1530
>>> do_new_mount+0x1dc/0x4e4 fs/namespace.c:3040
>>> path_mount+0x358/0x914 fs/namespace.c:3370
>>> do_mount fs/namespace.c:3383 [inline]
>>> __do_sys_mount fs/namespace.c:3591 [inline]
>>> __se_sys_mount fs/namespace.c:3568 [inline]
>>> __arm64_sys_mount+0x2f8/0x408 fs/namespace.c:3568
>>>
>>> Cc: <stable@...nel.org>
>>> Reported-by: syzbot+81684812ea68216e08c5@...kaller.appspotmail.com
>>> Signed-off-by: Chao Yu <chao.yu@...o.com>
>>
>> Reviewed-by: Muchun Song <songmuchun@...edance.com>
>>
>> Thanks.
>>
>>
>