[dm-devel] [PATCH 15/39] libmultipath: use fstat() when reading sysfs attributes

[Hannes Reinecke]

Coverity pointed out that we shouldn't be using stat()/open(),
as the file might have vanished or changed in between those
two calls. So modify it to open()/fstat() instead.

Signed-off-by: Hannes Reinecke <hare at suse.com>
---
 libmultipath/sysfs.c | 59 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 26 deletions(-)

diff --git a/libmultipath/sysfs.c b/libmultipath/sysfs.c
index de7df40..a74de9f 100644
--- a/libmultipath/sysfs.c
+++ b/libmultipath/sysfs.c
@@ -57,30 +57,31 @@ ssize_t sysfs_attr_get_value(struct udev_device *dev, const char *attr_name,
 	snprintf(devpath, PATH_SIZE, "%s/%s", udev_device_get_syspath(dev),
 		 attr_name);
 	condlog(4, "open '%s'", devpath);
-	if (stat(devpath, &statbuf) != 0) {
+	/* read attribute value */
+	fd = open(devpath, O_RDONLY);
+	if (fd < 0) {
+		condlog(4, "attribute '%s' can not be opened: %s",
+			devpath, strerror(errno));
+		return -errno;
+	}
+	if (fstat(fd, &statbuf) < 0) {
 		condlog(4, "stat '%s' failed: %s", devpath, strerror(errno));
+		close(fd);
 		return -ENXIO;
 	}
-
 	/* skip directories */
 	if (S_ISDIR(statbuf.st_mode)) {
 		condlog(4, "%s is a directory", devpath);
+		close(fd);
 		return -EISDIR;
 	}
-
 	/* skip non-writeable files */
 	if ((statbuf.st_mode & S_IRUSR) == 0) {
 		condlog(4, "%s is not readable", devpath);
+		close(fd);
 		return -EPERM;
 	}
 
-	/* read attribute value */
-	fd = open(devpath, O_RDONLY);
-	if (fd < 0) {
-		condlog(4, "attribute '%s' can not be opened: %s",
-			devpath, strerror(errno));
-		return -errno;
-	}
 	size = read(fd, value, value_len);
 	if (size < 0) {
 		condlog(4, "read from %s failed: %s", devpath, strerror(errno));
@@ -112,30 +113,33 @@ ssize_t sysfs_bin_attr_get_value(struct udev_device *dev, const char *attr_name,
 	snprintf(devpath, PATH_SIZE, "%s/%s", udev_device_get_syspath(dev),
 		 attr_name);
 	condlog(4, "open '%s'", devpath);
-	if (stat(devpath, &statbuf) != 0) {
+	/* read attribute value */
+	fd = open(devpath, O_RDONLY);
+	if (fd < 0) {
+		condlog(4, "attribute '%s' can not be opened: %s",
+			devpath, strerror(errno));
+		return -errno;
+	}
+	if (fstat(fd, &statbuf) != 0) {
 		condlog(4, "stat '%s' failed: %s", devpath, strerror(errno));
+		close(fd);
 		return -ENXIO;
 	}
 
 	/* skip directories */
 	if (S_ISDIR(statbuf.st_mode)) {
 		condlog(4, "%s is a directory", devpath);
+		close(fd);
 		return -EISDIR;
 	}
 
 	/* skip non-writeable files */
 	if ((statbuf.st_mode & S_IRUSR) == 0) {
 		condlog(4, "%s is not readable", devpath);
+		close(fd);
 		return -EPERM;
 	}
 
-	/* read attribute value */
-	fd = open(devpath, O_RDONLY);
-	if (fd < 0) {
-		condlog(4, "attribute '%s' can not be opened: %s",
-			devpath, strerror(errno));
-		return -errno;
-	}
 	size = read(fd, value, value_len);
 	if (size < 0) {
 		condlog(4, "read from %s failed: %s", devpath, strerror(errno));
@@ -163,30 +167,33 @@ ssize_t sysfs_attr_set_value(struct udev_device *dev, const char *attr_name,
 	snprintf(devpath, PATH_SIZE, "%s/%s", udev_device_get_syspath(dev),
 		 attr_name);
 	condlog(4, "open '%s'", devpath);
-	if (stat(devpath, &statbuf) != 0) {
+	/* write attribute value */
+	fd = open(devpath, O_WRONLY);
+	if (fd < 0) {
+		condlog(4, "attribute '%s' can not be opened: %s",
+			devpath, strerror(errno));
+		return -errno;
+	}
+	if (fstat(fd, &statbuf) != 0) {
 		condlog(4, "stat '%s' failed: %s", devpath, strerror(errno));
+		close(fd);
 		return -errno;
 	}
 
 	/* skip directories */
 	if (S_ISDIR(statbuf.st_mode)) {
 		condlog(4, "%s is a directory", devpath);
+		close(fd);
 		return -EISDIR;
 	}
 
 	/* skip non-writeable files */
 	if ((statbuf.st_mode & S_IWUSR) == 0) {
 		condlog(4, "%s is not writeable", devpath);
+		close(fd);
 		return -EPERM;
 	}
 
-	/* write attribute value */
-	fd = open(devpath, O_WRONLY);
-	if (fd < 0) {
-		condlog(4, "attribute '%s' can not be opened: %s",
-			devpath, strerror(errno));
-		return -errno;
-	}
 	size = write(fd, value, value_len);
 	if (size < 0) {
 		condlog(4, "write to %s failed: %s", devpath, strerror(errno));
-- 
2.6.6