On Mon, Jan 09, 2017 at 10:22:58AM -0500, Brian Foster wrote: > xfs_attr_[get|remove]() have unlocked attribute fork checks 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() > and xfs_attr_remove() already have the proper locking and checks further > down in the functions to handle this situation correctly. Drop the > unlocked checks to avoid the spurious failure and rely on the existing > logic. > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> > --- > Ping. Any chance of getting this one in soonish? Brian > v2: > - Fix up xfs_attr_remove() as well. > v1: https://patchwork.kernel.org/patch/9501675/ > > fs/xfs/libxfs/xfs_attr.c | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c > index af1ecb1..6622d46 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; > - > error = xfs_attr_args_init(&args, ip, name, flags); > if (error) > return error; > @@ -392,9 +389,6 @@ xfs_attr_remove( > if (XFS_FORCED_SHUTDOWN(dp->i_mount)) > return -EIO; > > - if (!xfs_inode_hasattr(dp)) > - return -ENOATTR; > - > error = xfs_attr_args_init(&args, dp, name, flags); > if (error) > return error; > -- > 2.7.4 > > -- > 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
