From: Stephen Hemminger <stephen@networkplumber.org>
Date: Tue, 2 Apr 2019 18:51:05 +0000 (-0700)
Subject: bus/pci: fix TOCTOU for sysfs access
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=c530aa78e3747cdd273310eeb9c50603da7f9cb6;p=dpdk.git

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 65f4896b9f..f240fe4f21 100644
--- 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);
 		}
 	}