bus/pci: fix TOCTOU for sysfs access

Using access followed by open causes a static analysis warning
about Time of check versus Time of use. Also, access() and
open() have different UID permission checks.

This is not a serious problem; but easy to fix by using errno instead.

Coverity issue: 300870
Fixes: 4a928ef9f611 ("bus/pci: enable write combining during mapping")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: David Marchand <david.marchand@redhat.com>

diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
index 65f4896..f240fe4 100644 (file)
--- a/drivers/bus/pci/linux/pci_uio.c
+++ b/drivers/bus/pci/linux/pci_uio.c
@@ -315,12 +315,11 @@ pci_uio_map_resource_by_index(struct rte_pci_device *dev, int res_idx,
                        loc->domain, loc->bus, loc->devid,
                        loc->function, res_idx);
 
-               if (access(devname, R_OK|W_OK) != -1) {
-                       fd = open(devname, O_RDWR);
-                       if (fd < 0)
-                               RTE_LOG(INFO, EAL, "%s cannot be mapped. "
-                                       "Fall-back to non prefetchable mode.\n",
-                                       devname);
+               fd = open(devname, O_RDWR);
+               if (fd < 0 && errno != ENOENT) {
+                       RTE_LOG(INFO, EAL, "%s cannot be mapped. "
+                               "Fall-back to non prefetchable mode.\n",
+                               devname);
                }
        }