[RFC,2/5] bus/pci: fix TOCTOU issue

Message ID 20181106214901.1392-3-stephen@networkplumber.org
State Superseded
Delegated to: Thomas Monjalon
Headers show
Series
  • more Coverity related bug fixes
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Checks

Context Check Description
ci/Intel-compilation success Compilation OK
ci/checkpatch success coding style OK

Commit Message

Stephen Hemminger Nov. 6, 2018, 9:48 p.m.
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")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/bus/pci/linux/pci_uio.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

Comments

Thomas Monjalon Nov. 18, 2018, 3:04 p.m. | #1
+Cc Ferruh

06/11/2018 22:48, Stephen Hemminger:
> 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")
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>  drivers/bus/pci/linux/pci_uio.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
> index 112ac51dddcc..8521fe63b0ae 100644
> --- a/drivers/bus/pci/linux/pci_uio.c
> +++ b/drivers/bus/pci/linux/pci_uio.c
> @@ -306,12 +306,11 @@ 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);
>  		}
>  	}

Patch

diff --git a/drivers/bus/pci/linux/pci_uio.c b/drivers/bus/pci/linux/pci_uio.c
index 112ac51dddcc..8521fe63b0ae 100644
--- a/drivers/bus/pci/linux/pci_uio.c
+++ b/drivers/bus/pci/linux/pci_uio.c
@@ -306,12 +306,11 @@  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);
 		}
 	}