On Wed, Feb 28, 2024 at 11:33:36AM -0800, Guenter Roeck wrote:
> On 2/28/24 11:26, Daniel Díaz wrote:
> > Hello!
> >
> > On Wed, 28 Feb 2024 at 12:19, Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> wrote:
> > > Kunit ext4_mballoc_test tests found following kernel oops on Linux next.
> > > All ways reproducible on all the architectures and steps to reproduce shared
> > > in the bottom of this email.
> > >
> > > Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> > >
>
> [ ... ]
>
> > +Guenter. Just the thing we were talking about, at about the same time.
> >
>
> Good that others see the same problem. Thanks a lot for reporting!
Hm...
static struct super_block *mbt_ext4_alloc_super_block(void)
{ struct ext4_super_block *es = kzalloc(sizeof(*es), GFP_KERNEL);
struct ext4_sb_info *sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
struct mbt_ext4_super_block *fsb = kzalloc(sizeof(*fsb), GFP_KERNEL);
if (fsb == NULL || sbi == NULL || es == NULL)
goto out;
sbi->s_es = es;
fsb->sb.s_fs_info = sbi;
return &fsb->sb;
out:
kfree(fsb);
kfree(sbi);
kfree(es);
return NULL;
}
That VFS level struct super_block that is returned from this function is
never really initialized afaict? Therefore, sb->s_user_ns == NULL:
i_uid_write(sb, ...)
-> NULL = i_user_ns(sb)
-> make_kuid(NULL)
-> map_id_range_down(NULL)
Outside of this test this can never be the case. See alloc_super() in
fs/super.c. So to stop the bleeding this needs something like:
static struct super_block *mbt_ext4_alloc_super_block(void)
{
struct ext4_super_block *es = kzalloc(sizeof(*es), GFP_KERNEL);
struct ext4_sb_info *sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
struct mbt_ext4_super_block *fsb = kzalloc(sizeof(*fsb), GFP_KERNEL);
if (fsb == NULL || sbi == NULL || es == NULL)
goto out;
sbi->s_es = es;
fsb->sb.s_fs_info = sbi;
+ fsb.sb.s_user_ns = &init_user_ns;
return &fsb->sb;
out:
kfree(fsb);
kfree(sbi);
kfree(es);
return NULL;
}
