On Thu, Aug 21, 2025 at 04:36:10PM -0500, Eric Sandeen wrote:

ENODATA (aka ENOATTR) has a very specific meaning in the xfs xattr code; namely, that the requested attribute name could not be found.

However, a medium error from disk may also return ENODATA. At best, this medium error may escape to userspace as "attribute not found" when in fact it's an IO (disk) error.

At worst, we may oops in xfs_attr_leaf_get() when we do:

error = xfs_attr_leaf_hasname(args, &bp); if (error == -ENOATTR) { xfs_trans_brelse(args->trans, bp); return error; }

because an ENODATA/ENOATTR error from disk leaves us with a null bp, and the xfs_trans_brelse will then null-deref it.

As discussed on the list, we really need to modify the lower level IO functions to trap all disk errors and ensure that we don't let unique errors like this leak up into higher xfs functions - many like this should be remapped to EIO.

However, this patch directly addresses a reported bug in the xattr code, and should be safe to backport to stable kernels. A larger-scope patch to handle more unique errors at lower levels can follow later.

(Note, prior to 07120f1abdff we did not oops, but we did return the wrong error code to userspace.)

Signed-off-by: Eric Sandeen sandeen@redhat.com Fixes: 07120f1abdff ("xfs: Add xfs_has_attr and subroutines") Cc: stable@vger.kernel.org # v5.9+

---

(I get it that sprinkling this around to 3 places might have an ick factor but I think it's necessary to make a surgical strike on this bug before we address the general problem.)

Thanks, -Eric

diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c index fddb55605e0c..9b54cfb0e13d 100644 --- a/fs/xfs/libxfs/xfs_attr_leaf.c +++ b/fs/xfs/libxfs/xfs_attr_leaf.c @@ -478,6 +478,12 @@ xfs_attr3_leaf_read( err = xfs_da_read_buf(tp, dp, bno, 0, bpp, XFS_ATTR_FORK, &xfs_attr3_leaf_buf_ops);

• /*

• * ENODATA from disk implies a disk medium failure; ENODATA for
  

• * xattrs means attribute not found, so disambiguate that here.
  

• */
  

• if (err == -ENODATA)

• err = -EIO;
  

I think this first chunk isn't needed since you also changed xfs_da_read_buf to filter the error code, right?

(Shifting towards the giant reconsideration of ENODATA -> EIO filtering)

Do we now also need to adjust the online fsck code to turn ENODATA into a corruption report? From __xchk_process_error:

case -EFSBADCRC: case -EFSCORRUPTED: /* Note the badness but don't abort. */ sc->sm->sm_flags |= errflag; *error = 0; fallthrough; default: trace_xchk_op_error(sc, agno, bno, *error, ret_ip); break; }

We only flag corruptions for these two error codes, but ENODATA from the block layer means "critical medium error". I take that to mean the media has permanently lost whatever was persisted there, right?

--D

if (err || !(*bpp)) return err; diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c index 4c44ce1c8a64..bff3dc226f81 100644 --- a/fs/xfs/libxfs/xfs_attr_remote.c +++ b/fs/xfs/libxfs/xfs_attr_remote.c @@ -435,6 +435,13 @@ xfs_attr_rmtval_get( 0, &bp, &xfs_attr3_rmt_buf_ops); if (xfs_metadata_is_sick(error)) xfs_dirattr_mark_sick(args->dp, XFS_ATTR_FORK);

• 	/*
  

• 	 * ENODATA from disk implies a disk medium failure;
  

• 	 * ENODATA for xattrs means attribute not found, so
  

• 	 * disambiguate that here.
  

• 	 */
  

• 	if (error == -ENODATA)
  

• 		error = -EIO;
  if (error)
  	return error;
  

diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c index 17d9e6154f19..723a0643b838 100644 --- a/fs/xfs/libxfs/xfs_da_btree.c +++ b/fs/xfs/libxfs/xfs_da_btree.c @@ -2833,6 +2833,12 @@ xfs_da_read_buf( &bp, ops); if (xfs_metadata_is_sick(error)) xfs_dirattr_mark_sick(dp, whichfork);

• /*

• * ENODATA from disk implies a disk medium failure; ENODATA for
  

• * xattrs means attribute not found, so disambiguate that here.
  

• */
  

• if (error == -ENODATA && whichfork == XFS_ATTR_FORK)

• error = -EIO;
  

  if (error) goto out_free;