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

[Chao Yu]

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@xxxxxxxxxx> 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@xxxxxxxx>
> > >
> > > 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@xxxxxxxxxx>
> > > Reported-by: syzbot+81684812ea68216e08c5@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Chao Yu <chao.yu@xxxxxxxx>
> >
> > Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> >
> > Thanks.