[PATCH] lib: fwts_cpu.c: fix time-of-use race on stat/open (LP: #1209225)

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

Coverity Scan reports that the stat/open may give a small window
of opportunity for a stat/open race condition. So just forget the
stat as open will do.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 src/lib/src/fwts_cpu.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/src/lib/src/fwts_cpu.c b/src/lib/src/fwts_cpu.c
index 44711fd..fc52fa5 100644
--- a/src/lib/src/fwts_cpu.c
+++ b/src/lib/src/fwts_cpu.c
@@ -51,30 +51,23 @@ static pid_t *fwts_cpu_pids;
  */
 int fwts_cpu_readmsr(const int cpu, const uint32_t reg, uint64_t *val)
 {
-	struct stat statbuf;
 	char buffer[PATH_MAX];
-	uint64_t value;
+	uint64_t value = 0;
 	int fd;
 	int ret;
 
-	value = 0;
-
 	snprintf(buffer, sizeof(buffer), "/dev/cpu/%d/msr", cpu);
-
-	if (stat(buffer, &statbuf)) {
+	if ((fd = open(buffer, O_RDONLY)) < 0) {
 		/* Hrm, msr not there, so force modprobe msr and see what happens */
 		pid_t pid;
 		if ((fd = fwts_pipe_open("modprobe msr", &pid)) < 0)
 			return FWTS_ERROR;
 		fwts_pipe_close(fd, pid);
 
-		if (stat(buffer, &statbuf))
+		if ((fd = open(buffer, O_RDONLY)) < 0)
 			return FWTS_ERROR; /* Really failed */
 	}
 
-	if ((fd = open(buffer, O_RDONLY)) < 0)
-                return FWTS_ERROR;
-
 	ret = pread(fd, &value, 8, reg);
 	close(fd);
 
-- 
1.8.3.2