From 4dbd00fc948efef8e8bbe4d52189e98701227948 Mon Sep 17 00:00:00 2001
From: Brad Barden <b+suckless@13os.net>
Date: Thu, 28 Jan 2016 15:53:36 -0600
Subject: [PATCH] mount: fix mount helper fs option handling

If a mount helper is used, only argopts (given on commandline) are
passed to the helper via -o parameter. Option strings from fstab are
ignored.

This patch replaces global argopts pointer with a character array
fsopts. A maximum length for filesytem options is #defined (used by
fsopts and data), and argument/mntent options are length-checked to fit.
A filesystem with too long an option string will print an error, cause
mount to exit with an error status, and not attempt to mount the
filesystem. This obviates the need for overflow checking of data in
parseopts(), though it hasn't been removed.
---
 mount.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/mount.c b/mount.c
index 8888c60..2a7773e 100644
--- a/mount.c
+++ b/mount.c
@@ -15,6 +15,8 @@
 #include "text.h"
 #include "util.h"
 
+#define FSOPTS_MAXLEN 512
+
 struct {
 	const char *opt;
 	const char *notopt;
@@ -37,7 +39,7 @@ struct {
 };
 
 static unsigned long argflags = 0;
-static char *argopts = NULL;
+static char fsopts[FSOPTS_MAXLEN] = "";
 
 static char *
 findtype(const char *types, const char *t)
@@ -121,9 +123,9 @@ mounthelper(const char *fsname, const char *dir, const char *fstype)
 		if (argflags & MS_REC)
 			eargv[i++] = "-R";
 
-		if (argopts) {
+		if (fsopts[0]) {
 			eargv[i++] = "-o";
-			eargv[i++] = argopts;
+			eargv[i++] = fsopts;
 		}
 		eargv[i++] = fsname;
 		eargv[i++] = dir;
@@ -188,11 +190,11 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	char *types = NULL, data[512] = "", *resolvpath = NULL;
+	char *types = NULL, data[FSOPTS_MAXLEN] = "", *resolvpath = NULL;
 	char *files[] = { "/proc/mounts", "/etc/fstab", NULL };
 	const char *source, *target;
 	struct mntent *me = NULL;
-	int aflag = 0, oflag = 0, status = 0, i, r;
+	int aflag = 0, status = 0, i, r;
 	unsigned long flags = 0;
 	FILE *fp;
 
@@ -210,9 +212,9 @@ main(int argc, char *argv[])
 		aflag = 1;
 		break;
 	case 'o':
-		oflag = 1;
-		argopts = EARGF(usage());
-		parseopts(argopts, &flags, data, sizeof(data));
+		if (strlcat(fsopts, EARGF(usage()), sizeof(fsopts)) >= sizeof(fsopts))
+			eprintf("option string too long\n");
+		parseopts(fsopts, &flags, data, sizeof(data));
 		break;
 	case 't':
 		types = EARGF(usage());
@@ -260,8 +262,10 @@ main(int argc, char *argv[])
 					target = me->mnt_dir;
 					source = me->mnt_fsname;
 				}
-				if (!oflag)
-					parseopts(me->mnt_opts, &flags, data, sizeof(data));
+				if (!fsopts[0])
+					if (strlcat(fsopts, me->mnt_opts, sizeof(fsopts)) >= sizeof(fsopts))
+						eprintf("%s: option string too long\n", target);
+					parseopts(fsopts, &flags, data, sizeof(data));
 				if (!types)
 					types = me->mnt_type;
 				goto mountsingle;
@@ -294,7 +298,13 @@ mountall:
 		if (hasmntopt(me, MNTOPT_NOAUTO) || mounted(me->mnt_dir))
 			continue;
 		flags = 0;
-		parseopts(me->mnt_opts, &flags, data, sizeof(data));
+		fsopts[0] = '\0';
+		if (strlcat(fsopts, me->mnt_opts, sizeof(fsopts)) >= sizeof(fsopts)) {
+			weprintf("%s: option string too long\n", me->mnt_dir);
+			status = 1;
+			continue;
+		}
+		parseopts(fsopts, &flags, data, sizeof(data));
 		/* if -t types specified:
 		 * if non-match, skip
 		 * if match and prefixed with "no", skip */