on 2/29/2024 6:09 PM, Christian Brauner wrote:
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@linaro.org 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@linaro.org
[ ... ]
+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; }
Hi Christian, Thanks for the information. I'm looking at this too and I also found root cause is sb.s_user_ns is NULL. I'm considering to get a super_block with VFS level api sget_fc to fix this to avoid similar problem when new unit tests are added or new member is added to super_block. Would like to hear more from you. Thanks!