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

[Chao Yu]

On 2022/9/10 0:47, Christophe JAILLET wrote:
> Le 30/08/2022 à 16:10, Chao Yu a écrit :
> > 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();
> >
> > 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>
> > ---
> >   mm/slub.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 862dbd9af4f5..e6f3727b9ad2 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -5890,7 +5890,8 @@ static char *create_unique_id(struct kmem_cache *s)
> >       char *name = kmalloc(ID_STR_LENGTH, GFP_KERNEL);
>
> Hi,
>
> looks that ID_STR_LENGTH could even be reduced to 32 or 16.
>
> The 2nd BUG_ON at the end of the function could certainly be just removed as well or remplaced by a:
>         if (p > name + ID_STR_LENGTH - 1) {
>          kfree(name);
>          return -E<something>;
>      }

Hi Christophe, Vlastimil,

Should I include this in v3? or may be in another patch?

Thanks,

> Just my 2c,
>
> CJ
>
> >       char *p = name;
> > -    BUG_ON(!name);
> > +    if (!name)
> > +        return ERR_PTR(-ENOMEM);
> >       *p++ = ':';
> >       /*
> > @@ -5948,6 +5949,8 @@ static int sysfs_slab_add(struct kmem_cache *s)
> >            * for the symlinks.
> >            */
> >           name = create_unique_id(s);
> > +        if (IS_ERR(name))
> > +            return PTR_ERR(name);
> >       }
> >       s->kobj.kset = kset;