mount.cifs: use lock/unlock_mtab scheme from util-linux-ng mount prog

The util-linux-ng sources have a good, but rather complex scheme for
locking the mtab before updating it. Mount helpers need to follow the
same scheme. Advisory locking only works if everyone is using the same
locking scheme.

Copy the routines we need from util-linux-ng into a separate source file
and then have mount.cifs and umount.cifs link in this object.

The long term goal is to have these routines in a separate helper
library (libmount). Mount helpers can then dynamically link in that lib.
Until that happens, this should serve as a suitable stopgap solution.

Signed-off-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 49 insertions, 48 deletions

diff --git a/source3/client/mount.cifs.c b/source3/client/mount.cifs.c
index 2a9c2b7304..da2f98bff8 100644
--- a/source3/client/mount.cifs.c
+++ b/source3/client/mount.cifs.c
@@ -39,9 +39,10 @@
 #include <mntent.h>
 #include <fcntl.h>
 #include <limits.h>
+#include "mount.h"
 
 #define MOUNT_CIFS_VERSION_MAJOR "1"
-#define MOUNT_CIFS_VERSION_MINOR "11"
+#define MOUNT_CIFS_VERSION_MINOR "12"
 
 #ifndef MOUNT_CIFS_VENDOR_SUFFIX
  #ifdef _SAMBA_BUILD_
@@ -79,15 +80,6 @@
 #define MOUNT_PASSWD_SIZE 64
 #define DOMAIN_SIZE 64
 
-/* exit status - bits below are ORed */
-#define EX_USAGE        1       /* incorrect invocation or permission */
-#define EX_SYSERR       2       /* out of memory, cannot fork, ... */
-#define EX_SOFTWARE     4       /* internal mount bug or wrong version */
-#define EX_USER         8       /* user interrupt */
-#define EX_FILEIO      16       /* problems writing, locking, ... mtab/fstab */
-#define EX_FAIL        32       /* mount failure */
-#define EX_SOMEOK      64       /* some mount succeeded */
-
 const char *thisprogram;
 int verboseflag = 0;
 static int got_password = 0;
@@ -1424,48 +1416,57 @@ mount_retry:
 		printf("Refer to the mount.cifs(8) manual page (e.g.man mount.cifs)\n");
 		rc = EX_FAIL;
 	} else {
+		atexit(unlock_mtab);
+		rc = lock_mtab();
+		if (rc) {
+			printf("cannot lock mtab");
+			goto mount_exit;
+		}
 		pmntfile = setmntent(MOUNTED, "a+");
-		if(pmntfile) {
-			mountent.mnt_fsname = dev_name;
-			mountent.mnt_dir = mountpoint;
-			mountent.mnt_type = CONST_DISCARD(char *,"cifs");
-			mountent.mnt_opts = (char *)malloc(220);
-			if(mountent.mnt_opts) {
-				char * mount_user = getusername();
-				memset(mountent.mnt_opts,0,200);
-				if(flags & MS_RDONLY)
-					strlcat(mountent.mnt_opts,"ro",220);
-				else
-					strlcat(mountent.mnt_opts,"rw",220);
-				if(flags & MS_MANDLOCK)
-					strlcat(mountent.mnt_opts,",mand",220);
-				if(flags & MS_NOEXEC)
-					strlcat(mountent.mnt_opts,",noexec",220);
-				if(flags & MS_NOSUID)
-					strlcat(mountent.mnt_opts,",nosuid",220);
-				if(flags & MS_NODEV)
-					strlcat(mountent.mnt_opts,",nodev",220);
-				if(flags & MS_SYNCHRONOUS)
-					strlcat(mountent.mnt_opts,",synch",220);
-				if(mount_user) {
-					if(getuid() != 0) {
-						strlcat(mountent.mnt_opts,",user=",220);
-						strlcat(mountent.mnt_opts,mount_user,220);
-					}
-					/* free(mount_user); do not free static mem */
-				}
-			}
-			mountent.mnt_freq = 0;
-			mountent.mnt_passno = 0;
-			rc = addmntent(pmntfile,&mountent);
-			endmntent(pmntfile);
-			SAFE_FREE(mountent.mnt_opts);
-			if (rc)
-				rc = EX_FILEIO;
-		} else {
+		if (!pmntfile) {
 			printf("could not update mount table\n");
+			unlock_mtab();
 			rc = EX_FILEIO;
+			goto mount_exit;
 		}
+		mountent.mnt_fsname = dev_name;
+		mountent.mnt_dir = mountpoint;
+		mountent.mnt_type = CONST_DISCARD(char *,"cifs");
+		mountent.mnt_opts = (char *)malloc(220);
+		if(mountent.mnt_opts) {
+			char * mount_user = getusername();
+			memset(mountent.mnt_opts,0,200);
+			if(flags & MS_RDONLY)
+				strlcat(mountent.mnt_opts,"ro",220);
+			else
+				strlcat(mountent.mnt_opts,"rw",220);
+			if(flags & MS_MANDLOCK)
+				strlcat(mountent.mnt_opts,",mand",220);
+			if(flags & MS_NOEXEC)
+				strlcat(mountent.mnt_opts,",noexec",220);
+			if(flags & MS_NOSUID)
+				strlcat(mountent.mnt_opts,",nosuid",220);
+			if(flags & MS_NODEV)
+				strlcat(mountent.mnt_opts,",nodev",220);
+			if(flags & MS_SYNCHRONOUS)
+				strlcat(mountent.mnt_opts,",sync",220);
+			if(mount_user) {
+				if(getuid() != 0) {
+					strlcat(mountent.mnt_opts,
+						",user=", 220);
+					strlcat(mountent.mnt_opts,
+						mount_user, 220);
+				}
+			}
+		}
+		mountent.mnt_freq = 0;
+		mountent.mnt_passno = 0;
+		rc = addmntent(pmntfile,&mountent);
+		endmntent(pmntfile);
+		unlock_mtab();
+		SAFE_FREE(mountent.mnt_opts);
+		if (rc)
+			rc = EX_FILEIO;
 	}
 mount_exit:
 	if(mountpassword) {