[PATCH 4/4] bus/pci/bsd: Fix device existence check

[Jake Freeland]

Use open(2) instead of access(2) to check for the existence of the target
device. This avoids a possible race condition where the the device file is
removed after a successful call to access(2) but before open(2).

This also fixes any potential bugs associated with passing open(2)-style
flags into access(2). i.e. access(2) does not formally support the O_RDWR
flag.

Signed-off-by: Jake Freeland <jfree at FreeBSD.org>
---
 drivers/bus/pci/bsd/pci.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/bus/pci/bsd/pci.c b/drivers/bus/pci/bsd/pci.c
index c64cd2c86c..9bce9df503 100644
--- a/drivers/bus/pci/bsd/pci.c
+++ b/drivers/bus/pci/bsd/pci.c
@@ -106,20 +106,29 @@ pci_uio_alloc_resource(struct rte_pci_device *dev,
 {
 	char devname[PATH_MAX]; /* contains the /dev/uioX */
 	struct rte_pci_addr *loc;
+	int fd;
 
 	loc = &dev->addr;
 
 	snprintf(devname, sizeof(devname), "/dev/uio at pci:%u:%u:%u",
 			dev->addr.bus, dev->addr.devid, dev->addr.function);
 
-	if (access(devname, O_RDWR) < 0) {
-		PCI_LOG(WARNING, "  "PCI_PRI_FMT" not managed by UIO driver, skipping",
-			loc->domain, loc->bus, loc->devid, loc->function);
-		return 1;
+	fd = open(devname, O_RDWR);
+	if (fd < 0) {
+		if (errno == ENOENT) {
+			PCI_LOG(WARNING, PCI_PRI_FMT" not managed by UIO "
+					"driver, skipping", loc->domain,
+					loc->bus, loc->devid, loc->function);
+			return 1;
+		}
+		PCI_LOG(ERR, "Failed to open device file for " PCI_PRI_FMT
+				" (%s)", loc->domain, loc->bus, loc->devid,
+				loc->function, devname);
+		return -1;
 	}
 
 	/* save fd if in primary process */
-	if (rte_intr_fd_set(dev->intr_handle, open(devname, O_RDWR))) {
+	if (rte_intr_fd_set(dev->intr_handle, fd)) {
 		PCI_LOG(WARNING, "Failed to save fd");
 		goto error;
 	}
-- 
2.47.2