diff mbox series

Fix search for device ID in tst_find_backing_dev()

Message ID 20200925102724.25815-1-mdoucha@suse.cz
State Accepted
Headers show
Series Fix search for device ID in tst_find_backing_dev() | expand

Commit Message

Martin Doucha Sept. 25, 2020, 10:27 a.m. UTC 
The current search using substrings can lead to false positives, e.g. search
for device 0:5 could return device 10:50 instead. Parse device IDs in
/proc/self/mountinfo properly using sscanf() and also check whether the device
was really found.

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
---
 lib/tst_device.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Martin Doucha Sept. 25, 2020, 10:31 a.m. UTC | #1 
On 25. 09. 20 12:27, Martin Doucha wrote:
> The current search using substrings can lead to false positives, e.g. search
> for device 0:5 could return device 10:50 instead. Parse device IDs in
> /proc/self/mountinfo properly using sscanf() and also check whether the device
> was really found.
> 
> Signed-off-by: Martin Doucha <mdoucha@suse.cz>

I forgot to add an extra comment that I still don't like that the search
uses fixed-size buffer without properly handling lines that are too long
but let's keep the fix simple for now. We can fix long line handling
after the release.
Cyril Hrubis Sept. 25, 2020, 1:01 p.m. UTC | #2 
Hi!
Applied, thanks.
diff mbox series

Patch

diff --git a/lib/tst_device.c b/lib/tst_device.c
index 0e98a7280..c096b418b 100644
--- a/lib/tst_device.c
+++ b/lib/tst_device.c
@@ -497,21 +497,26 @@  unsigned long tst_dev_bytes_written(const char *dev)
 
 void tst_find_backing_dev(const char *path, char *dev)
 {
-	char fmt[20];
 	struct stat buf;
 	FILE *file;
 	char line[PATH_MAX];
 	char *pre = NULL;
 	char *next = NULL;
+	unsigned int dev_major, dev_minor, line_mjr, line_mnr;
 
 	if (stat(path, &buf) < 0)
 		tst_brkm(TWARN | TERRNO, NULL, "stat() failed");
 
-	snprintf(fmt, sizeof(fmt), "%u:%u", major(buf.st_dev), minor(buf.st_dev));
+	dev_major = major(buf.st_dev);
+	dev_minor = minor(buf.st_dev);
 	file = SAFE_FOPEN(NULL, "/proc/self/mountinfo", "r");
+	*dev = '\0';
 
 	while (fgets(line, sizeof(line), file)) {
-		if (strstr(line, fmt) != NULL) {
+		if (sscanf(line, "%*d %*d %d:%d", &line_mjr, &line_mnr) != 2)
+			continue;
+
+		if (line_mjr == dev_major && line_mnr == dev_minor) {
 			pre = strstr(line, " - ");
 			pre = strtok_r(pre, " ", &next);
 			pre = strtok_r(NULL, " ", &next);
@@ -523,8 +528,11 @@  void tst_find_backing_dev(const char *path, char *dev)
 
 	SAFE_FCLOSE(NULL, file);
 
+	if (!*dev)
+		tst_brkm(TBROK, NULL, "Cannot find block device for %s", path);
+
 	if (stat(dev, &buf) < 0)
-		 tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
+		tst_brkm(TWARN | TERRNO, NULL, "stat(%s) failed", dev);
 
 	if (S_ISBLK(buf.st_mode) != 1)
 		tst_brkm(TCONF, NULL, "dev(%s) isn't a block dev", dev);