From: Eric Sandeen Date: Wed, 19 Aug 2015 00:30:48 +0000 (+1000) Subject: xfs: set XFS_DA_OP_OKNOENT in xfs_attr_get X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=c400ee3ed1b13d45adde68e12254dc6ab6977b59;p=openwrt%2Fstaging%2Fblogic.git xfs: set XFS_DA_OP_OKNOENT in xfs_attr_get It's entirely possible for userspace to ask for an xattr which does not exist. Normally, there is no problem whatsoever when we ask for such a thing, but when we look at an obfuscated metadump image on a debug kernel with selinux, we trip over this ASSERT in xfs_da3_path_shift(): *result = -ENOENT; /* we're out of our tree */ ASSERT(args->op_flags & XFS_DA_OP_OKNOENT); It (more or less) only shows up in the above scenario, because xfs_metadump obfuscates attr names, but chooses names which keep the same hash value - and xfs_da3_node_lookup_int does: if (((retval == -ENOENT) || (retval == -ENOATTR)) && (blk->hashval == args->hashval)) { error = xfs_da3_path_shift(state, &state->path, 1, 1, &retval); IOWS, we only get down to the xfs_da3_path_shift() ASSERT if we are looking for an xattr which doesn't exist, but we find xattrs on disk which have the same hash, and so might be a hash collision, so we try the path shift. When *that* fails to find what we're looking for, we hit the assert about XFS_DA_OP_OKNOENT. Simply setting XFS_DA_OP_OKNOENT in xfs_attr_get solves this rather corner-case problem with no ill side effects. It's fine for an attr name lookup to fail. Signed-off-by: Eric Sandeen Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c index 3349c9a1e845..ff065578969f 100644 --- a/fs/xfs/libxfs/xfs_attr.c +++ b/fs/xfs/libxfs/xfs_attr.c @@ -139,6 +139,8 @@ xfs_attr_get( args.value = value; args.valuelen = *valuelenp; + /* Entirely possible to look up a name which doesn't exist */ + args.op_flags = XFS_DA_OP_OKNOENT; lock_mode = xfs_ilock_attr_map_shared(ip); if (!xfs_inode_hasattr(ip))