On Sun, Jan 08, 2017 at 07:30:08AM -0800, Christoph Hellwig wrote: > On Fri, Jan 06, 2017 at 02:37:12PM -0500, Brian Foster wrote: > > xfs_attr_get() has an unlocked attribute fork check to optimize away a > > lock cycle in cases where the fork does not exist or is otherwise empty. > > This check is not safe, however, because an attribute fork short form to > > extent format conversion includes a transient state that causes the > > xfs_inode_hasattr() check to fail. Specifically, > > xfs_attr_shortform_to_leaf() creates an empty extent format attribute > > fork and then adds the existing shortform attributes to it. > > > > This means that lookup of an existing xattr can spuriously return > > -ENOATTR when racing against a setxattr that causes the associated > > format conversion. This was originally reproduced by an untar on a > > particularly configured glusterfs volume, but can also be reproduced on > > demand with properly crafted xattr requests. > > > > The format conversion occurs under the exclusive ilock. xfs_attr_get() > > already has the proper locking and checks further down in the function > > to handle this situation correctly. Drop the unlocked check to avoid the > > spurious failure and rely on the existing logic. > > > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> > > --- > > > > This survives a local xfstests run and the original glusterfs > > reproducer. I also have an xfstests reproducer that I will post shortly. > > > > Brian > > > > fs/xfs/libxfs/xfs_attr.c | 3 --- > > 1 file changed, 3 deletions(-) > > > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c > > index af1ecb1..8fcbc52 100644 > > --- a/fs/xfs/libxfs/xfs_attr.c > > +++ b/fs/xfs/libxfs/xfs_attr.c > > @@ -131,9 +131,6 @@ xfs_attr_get( > > if (XFS_FORCED_SHUTDOWN(ip->i_mount)) > > return -EIO; > > > > - if (!xfs_inode_hasattr(ip)) > > - return -ENOATTR; > > - > > What about the similar pre-lock check in xfs_attr_remove? Yep, will fix. Thanks for catching that.. Brian > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
