staging/lustre/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.

Signed-off-by: Christopher J. Morrone <morrone2@llnl.gov>
Reviewed-on: http://review.whamcloud.com/11989
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5150
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c b/drivers/staging/lustre/lustre/mdc/mdc_request.c
index c04eec5c603e99c40ec42d4df93490f26b447754..f8ef5fe5e771d091f49e53026f61f36a6e2823f8 100644 (file)
--- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
+++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
@@ -481,6 +481,9 @@ 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->aclsize);
+       if (acl == NULL)
+               return 0;
+
        if (IS_ERR(acl)) {
                rc = PTR_ERR(acl);
                CERROR("convert xattr to acl: %d\n", rc);