From a4c0cc75ff9744299f108c259efab1bd30c8007a Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Mon, 2 Jan 2012 11:08:17 +0100
Subject: [PATCH] mount: append inverting options for mount.<type>

 fstab:
	server://foo   /mnt/foo    nfs    user,exec

The mount(8) does not append the option "exec" to /sbin/mount.<type>
helper's command line. This is no problem when executed by non-root
user as it reads the options from fstab only.

.. but when executed by root (UID=0) then the mount.<type> helper
follows the command where the "exec" option is missing. This is bug.

original version (strace output):

 execve("/sbin/mount.nfs", ["/sbin/mount.nfs",
        "sr.net.home:/mnt/store", "/mnt/store", "-o",
        "rw,nosuid,nodev,noauto,user"], [/* 21 vars */]) = 0

fixed version:

 execve("/sbin/mount.nfs", ["/sbin/mount.nfs",
        "sr.net.home:/mnt/store", "/mnt/store", "-o",
        "rw,nosuid,nodev,noauto,user,exec"], [/* 21 vars */]) = 0
                                    ^^^^^

Signed-off-by: Karel Zak <kzak@redhat.com>
---
 mount/mount.c |   31 ++++++++++++++++++++++++-------
 1 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/mount/mount.c b/mount/mount.c
index 9b444c4..a18b2df 100644
--- a/mount/mount.c
+++ b/mount/mount.c
@@ -207,6 +207,8 @@ static const struct opt_map opt_map[] = {
 
 static int opt_nofail = 0;
 
+static int invuser_flags;
+
 static const char *opt_loopdev, *opt_vfstype, *opt_offset, *opt_sizelimit,
         *opt_encryption, *opt_speed, *opt_comment, *opt_uhelper, *opt_helper;
 
@@ -473,7 +475,7 @@ static int has_context_option(char *opts)
  * For the options uid= and gid= replace user or group name by its value.
  */
 static inline void
-parse_opt(char *opt, int *mask, char **extra_opts) {
+parse_opt(char *opt, int *mask, int *inv_user, char **extra_opts) {
 	const struct opt_map *om;
 
 	for (om = opt_map; om->opt != NULL; om++)
@@ -482,6 +484,9 @@ parse_opt(char *opt, int *mask, char **extra_opts) {
 				*mask &= ~om->mask;
 			else
 				*mask |= om->mask;
+			if (om->inv && ((*mask & MS_USER) || (*mask & MS_USERS))
+			    && (om->mask & MS_SECURE))
+				*inv_user |= om->mask;
 			if ((om->mask == MS_USER || om->mask == MS_USERS)
 			    && !om->inv)
 				*mask |= MS_SECURE;
@@ -566,7 +571,7 @@ parse_opts (const char *options, int *flags, char **extra_opts) {
 			/* end of option item or last item */
 			if (*p == '\0' || *(p+1) == '\0') {
 				if (!parse_string_opt(opt))
-					parse_opt(opt, flags, extra_opts);
+					parse_opt(opt, flags, &invuser_flags, extra_opts);
 				opt = NULL;
 			}
 		}
@@ -587,7 +592,9 @@ parse_opts (const char *options, int *flags, char **extra_opts) {
 
 /* Try to build a canonical options string.  */
 static char *
-fix_opts_string (int flags, const char *extra_opts, const char *user) {
+fix_opts_string (int flags, const char *extra_opts,
+		 const char *user, int inv_user)
+{
 	const struct opt_map *om;
 	const struct string_opt_map *m;
 	char *new_opts;
@@ -611,6 +618,16 @@ fix_opts_string (int flags, const char *extra_opts, const char *user) {
 	if (user)
 		new_opts = append_opt(new_opts, "user=", user);
 
+	if (inv_user) {
+		for (om = opt_map; om->opt != NULL; om++) {
+			if (om->mask && om->inv
+			    && (inv_user & om->mask) == om->mask) {
+				new_opts = append_opt(new_opts, om->opt, NULL);
+				inv_user &= ~om->mask;
+			}
+		}
+	}
+
 	return new_opts;
 }
 
@@ -662,7 +679,7 @@ create_mtab (void) {
 		mnt.mnt_dir = "/";
 		mnt.mnt_fsname = spec_to_devname(fstab->m.mnt_fsname);
 		mnt.mnt_type = fstab->m.mnt_type;
-		mnt.mnt_opts = fix_opts_string (flags, extra_opts, NULL);
+		mnt.mnt_opts = fix_opts_string (flags, extra_opts, NULL, 0);
 		mnt.mnt_freq = mnt.mnt_passno = 0;
 		free(extra_opts);
 
@@ -787,7 +804,7 @@ check_special_mountprog(const char *spec, const char *node, const char *type, in
 			if (setuid(getuid()) < 0)
 				die(EX_FAIL, _("mount: cannot set user id: %s"), strerror(errno));
 
-			oo = fix_opts_string (flags, extra_opts, NULL);
+			oo = fix_opts_string(flags, extra_opts, NULL, invuser_flags);
 			mountargs[i++] = mountprog;			/* 1 */
 			mountargs[i++] = (char *) spec;			/* 2 */
 			mountargs[i++] = (char *) node;			/* 3 */
@@ -1659,7 +1676,7 @@ try_mount_one (const char *spec0, const char *node0, const char *types0,
   }
 
 #ifdef HAVE_LIBMOUNT_MOUNT
-  mtab_opts = fix_opts_string(flags & ~MS_NOMTAB, extra_opts, user);
+  mtab_opts = fix_opts_string(flags & ~MS_NOMTAB, extra_opts, user, 0);
   mtab_flags = flags;
 
   if (fake)
@@ -1703,7 +1720,7 @@ try_mount_one (const char *spec0, const char *node0, const char *types0,
   }
 
   if (fake || mnt5_res == 0) {
-      char *mo = fix_opts_string (flags & ~MS_NOMTAB, extra_opts, user);
+      char *mo = fix_opts_string (flags & ~MS_NOMTAB, extra_opts, user, 0);
       const char *tp = types ? types : "unknown";
 
       /* Mount succeeded, report this (if verbose) and write mtab entry.  */
-- 
1.7.7.5