Re: [ramfs] 0858d7da8a: canonical_address#:#[##]

[yangerkun]

Cc ntfs3:

Maybe it's a problem like this:

do_new_mount
  fs_context_for_mount
    alloc_fs_context
      ntfs_init_fs_context
        sbi = kzalloc(sizeof(struct ntfs_sb_info), GFP_NOFS);
        fc->s_fs_info = sbi;
  vfs_get_tree
    ntfs_fs_get_tree
      get_tree_bdev
        blkdev_get_by_path  // return error and sbi->sb will be NULL
  put_fs_context
    ntfs_fs_free
      put_ntfs
        ntfs_update_mftmirr
          struct super_block *sb = sbi->sb; // NULL
          u32 blocksize = sb->s_blocksize; // BOOM

It's actually a ntfs3 bug which may be introduced by:

610f8f5a7baf fs/ntfs3: Use new api for mounting


On 2021/11/26 2:03, Linus Torvalds wrote:
> On Thu, Nov 25, 2021 at 6:08 AM kernel test robot <oliver.sang@xxxxxxxxx> wrote:
> > FYI, we noticed the following commit (built with clang-14):
> >
> > commit: 0858d7da8a09e440fb192a0239d20249a2d16af8 ("ramfs: fix mount source show for ramfs")
>
> Funky. That commit seems to have nothing to do with the oops:
>
> > [  806.257788][  T204] /dev/root: Can't open blockdev
> > [  806.259101][  T204] general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASAN
> > [  806.263082][  T204] KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
>
> Not a very helpful error message,a nd the KASAN comment makes little sense, but
>
> > [ 806.267540][ T204] RIP: 0010:ntfs_update_mftmirr (kbuild/src/consumer/fs/ntfs3/fsntfs.c:834)
>
> That's
>
>          u32 blocksize = sb->s_blocksize;
>
> and presumably with KASAN you end up getting hat odd 0xdffffc0000000003 thing.
>
> Anyway, looks like sb is NULL, and the code is
>
>    int ntfs_update_mftmirr(struct ntfs_sb_info *sbi, int wait)
>    {
>          int err;
>          struct super_block *sb = sbi->sb;
>          u32 blocksize = sb->s_blocksize;
>          sector_t block1, block2;
>
> although I have no idea how sbi->sb could be NULL.
>
> Konstantin? See
>
>      https://lore.kernel.org/lkml/20211125140816.GC3109@xsang-OptiPlex-9020/
>
> for the full thing.
>
>               Linus
> .