Fix getmntpoint(3) to operate as it is documented in its manual page.

The -libutil function getmntpoint(3) is documented as accepting a device name “with or without /dev/ prepended to it” but did not attempt to prepend /dev/. This patch corrects the problem by prepending /dev/ to names that do not begin with a '/'. Reported-by: Dag-Erling Smørgrav Differential Revision: https://reviews.freebsd.org/D53185 MFC-after: 1 week Sponsored-by: Netflix 

1 files changed, 37 insertions, 16 deletions

diff --git a/lib/libutil/mntopts.c b/lib/libutil/mntopts.c
index 07d3dd6d98a3..4a064a086fd5 100644
--- a/lib/libutil/mntopts.c
+++ b/lib/libutil/mntopts.c
@@ -145,6 +145,18 @@ checkpath_allow_file(const char *path, char *resolved)
	return (0);
 }
 
+static char *
+prependdevtopath(const char *path, char *buf, u_long buflen)
+{
+	u_long len;
+
+	if ((len = strlen(_PATH_DEV) + strlen(path) + 1) > buflen)
+	return NULL;
+	strncpy(buf, _PATH_DEV, len);
+	strncat(buf, path, len - sizeof(_PATH_DEV));
+	return (buf);
+}
+
 /*
 * Get the mount point information for name. Name may be mount point name
 * or device name (with or without /dev/ preprended).
@@ -153,19 +165,27 @@ struct statfs *
 getmntpoint(const char *name)
 {
	struct stat devstat, mntdevstat;
-	char device[sizeof(_PATH_DEV) - 1 + MNAMELEN];
-	char *ddevname;
+	char *devname;
	struct statfs *mntbuf, *statfsp;
-	int i, mntsize, isdev;
-	u_long len;
+	int i, len, isdev, mntsize, mntfromnamesize;
+	char device[sizeof(_PATH_DEV) - 1 + MNAMELEN];
+	u_long devlen;
 
-	if (stat(name, &devstat) != 0)
+	devlen = sizeof(device);
+	/*
+ * Note that stat(NULL, &statbuf) returns -1 (EBADF) which will
+ * cause us to return NULL if prependdevtopath() returns NULL.
+ */
+	if (stat(name, &devstat) != 0 &&
+ (name[0] != '/' &&
+ stat(prependdevtopath(name, device, devlen), &devstat) != 0))
	return (NULL);
	if (S_ISCHR(devstat.st_mode) || S_ISBLK(devstat.st_mode))
	isdev = 1;
	else
	isdev = 0;
	mntsize = getmntinfo(&mntbuf, MNT_NOWAIT);
+	mntfromnamesize = sizeof(statfsp->f_mntfromname);
	for (i = 0; i < mntsize; i++) {
	statfsp = &mntbuf[i];
	if (isdev == 0) {
@@ -173,19 +193,20 @@ getmntpoint(const char *name)
	continue;
	return (statfsp);
	}
-	ddevname = statfsp->f_mntfromname;
-	if (*ddevname != '/') {
-	if ((len = strlen(_PATH_DEV) + strlen(ddevname) + 1) >
- sizeof(statfsp->f_mntfromname) ||
- len > sizeof(device))
+	devname = statfsp->f_mntfromname;
+	if (*devname == '/') {
+	if (stat(devname, &mntdevstat) != 0)
+	continue;
+	} else {
+	devname = prependdevtopath(devname, device, devlen);
+	if (devname == NULL ||
+ (len = strlen(devname)) > mntfromnamesize)
+	continue;
+	if (stat(devname, &mntdevstat) != 0)
	continue;
-	strncpy(device, _PATH_DEV, len);
-	strncat(device, ddevname, len);
-	if (stat(device, &mntdevstat) == 0)
-	strncpy(statfsp->f_mntfromname, device, len);
+	strncpy(statfsp->f_mntfromname, devname, len);
	}
-	if (stat(ddevname, &mntdevstat) == 0 &&
- S_ISCHR(mntdevstat.st_mode) &&
+	if (S_ISCHR(mntdevstat.st_mode) &&
 mntdevstat.st_rdev == devstat.st_rdev)
	return (statfsp);
	}