vfio: fix group descriptor check

[ upstream commit 1f16fa9 ]

The issue is that a file descriptor at 0 is a valid one. Currently
the file not found, the return value will be set to 0. As a result,
it is impossible to distinguish between a correct descriptor and a
failed return value. Fix it to return -ENOENT instead of 0.

Fixes: b758423 ("vfio: fix race condition with sysfs")
Fixes: ff0b67d ("vfio: DMA mapping")

Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>

lib/librte_eal/linuxapp/eal/eal_vfio.c

@@ -292,7 +292,7 @@ vfio_open_group_fd(int iommu_group_num)
 							strerror(errno));
 					return -1;
 				}
-				return 0;
+				return -ENOENT;
 			}
 			/* noiommu group found */
 		}
@@ -317,12 +317,12 @@ vfio_open_group_fd(int iommu_group_num)
 			vfio_group_fd = mp_rep->fds[0];
 		} else if (p->result == SOCKET_NO_FD) {
 			RTE_LOG(ERR, EAL, "  bad VFIO group fd\n");
-			vfio_group_fd = 0;
+			vfio_group_fd = -ENOENT;
 		}
 	}
 
 	free(mp_reply.msgs);
-	if (vfio_group_fd < 0)
+	if (vfio_group_fd < 0 && vfio_group_fd != -ENOENT)
 		RTE_LOG(ERR, EAL, "  cannot request group fd\n");
 	return vfio_group_fd;
 }
@@ -378,9 +378,9 @@ vfio_get_group_fd(struct vfio_config *vfio_cfg,
 	}
 
 	vfio_group_fd = vfio_open_group_fd(iommu_group_num);
-	if (vfio_group_fd <= 0) {
+	if (vfio_group_fd < 0) {
 		RTE_LOG(ERR, EAL, "Failed to open group %d\n", iommu_group_num);
-		return -1;
+		return vfio_group_fd;
 	}
 
 	cur_grp->group_num = iommu_group_num;
@@ -704,11 +704,14 @@ rte_vfio_setup_device(const char *sysfs_base, const char *dev_addr,
 
 	/* get the actual group fd */
 	vfio_group_fd = rte_vfio_get_group_fd(iommu_group_num);
-	if (vfio_group_fd < 0)
+	if (vfio_group_fd < 0 && vfio_group_fd != -ENOENT)
 		return -1;
 
-	/* if group_fd == 0, that means the device isn't managed by VFIO */
-	if (vfio_group_fd == 0) {
+	/*
+	 * if vfio_group_fd == -ENOENT, that means the device
+	 * isn't managed by VFIO
+	 */
+	if (vfio_group_fd == -ENOENT) {
 		RTE_LOG(WARNING, EAL, " %s not managed by VFIO driver, skipping\n",
 				dev_addr);
 		return 1;
@@ -928,10 +931,10 @@ rte_vfio_release_device(const char *sysfs_base, const char *dev_addr,
 
 	/* get the actual group fd */
 	vfio_group_fd = rte_vfio_get_group_fd(iommu_group_num);
-	if (vfio_group_fd <= 0) {
+	if (vfio_group_fd < 0) {
 		RTE_LOG(INFO, EAL, "rte_vfio_get_group_fd failed for %s\n",
 				   dev_addr);
-		ret = -1;
+		ret = vfio_group_fd;
 		goto out;
 	}
 

lib/librte_eal/linuxapp/eal/eal_vfio_mp_sync.c

@@ -43,9 +43,9 @@ vfio_mp_primary(const struct rte_mp_msg *msg, const void *peer)
 		r->req = SOCKET_REQ_GROUP;
 		r->group_num = m->group_num;
 		fd = rte_vfio_get_group_fd(m->group_num);
-		if (fd < 0)
+		if (fd < 0 && fd != -ENOENT)
 			r->result = SOCKET_ERR;
-		else if (fd == 0)
+		else if (fd == -ENOENT)
 			/* if VFIO group exists but isn't bound to VFIO driver */
 			r->result = SOCKET_NO_FD;
 		else {