nfs: Check for null buf, and set op_errno to EIO not 0

Summary:
- Prevent crashes for the case where "getattr" actually failed and
  returned with a NULL buf, but the op_errno was set to 0.
- This is a cherry-pick of D1571184

Signed-off-by: Shreyas Siravara <sshreyas@fb.com>
Change-Id: Ia2d6ad7539df714f9420dcf063c7c14e727bb7e3
BUG: 1428064
Reviewed-on: http://review.gluster.org/16152
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Kevin Vigor <kvigor@fb.com>
Reviewed-on: https://review.gluster.org/16803
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Jeff Darcy <jeff@pl.atyp.us>
Reviewed-by: Jeff Darcy <jeff@pl.atyp.us>

1 files changed, 6 insertions, 0 deletions

diff --git a/xlators/nfs/server/src/nfs3.c b/xlators/nfs/server/src/nfs3.c
index 729f811c917..6399d624ff8 100644
--- a/xlators/nfs/server/src/nfs3.c
+++ b/xlators/nfs/server/src/nfs3.c
@@ -862,6 +862,12 @@ nfs3svc_getattr_stat_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
         cs = frame->local;
 
         if (op_ret == -1) {
+                /* Prevent crashes for the case where this call fails
+                 * and buf is left in a NULL state, yet the op_errno == 0.
+                 */
+                if (!buf && op_errno == 0) {
+                        op_errno = EIO;
+                }
                 status = nfs3_cbk_errno_status (op_ret, op_errno);
         }