LU-5150 mdc: Handle empty but non-zero acl xattr

We have found that posix_acl_access can have a value
of \002\000\000\000.  In that case body->aclsize is
non-zero, but the there are no actuall acls stored
in the xattr.

In mdc_unpack_acl(), it only checks IS_ERR() on the
pointer returned by posix_acl_from_xattr(), it does not
check for NULL.  Because of the above situation, the
xattr aclsize can be non-zero, but posic_acl_from_xattr()
still returns NULL.  Passing NULL to posix_acl_valid()
crashes the kernel.

We add a check to properly handle the NULL return value.

Change-Id: Ib4f623642b86db2c88923a27cd9e77c870f301af
Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/10620
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/mdc/mdc_request.c b/lustre/mdc/mdc_request.c
index f9e2b09..4bee7c2 100644 (file)
--- a/lustre/mdc/mdc_request.c
+++ b/lustre/mdc/mdc_request.c
@@ -463,6 +463,8 @@ static int mdc_unpack_acl(struct ptlrpc_request *req, struct lustre_md *md)
                RETURN(-EPROTO);
 
        acl = posix_acl_from_xattr(&init_user_ns, buf, body->mbo_aclsize);
+       if (acl == NULL)
+               RETURN(0);
         if (IS_ERR(acl)) {
                 rc = PTR_ERR(acl);
                 CERROR("convert xattr to acl: %d\n", rc);