Passthrough options starting with "x-" to mtab (#894)

This implements #651, tested with bindfs.

"x-*" options are comments meant to be interpreted by userspace.

#651 is about some 3rd party mount options like 'x-gvfs-notrash'.

This also removes the test if /etc/mtab is a symlink.

This test was added in commit 5f28cd15ab43c741f6d116be4d3a9aa5d82ab385
and the corresponding ChangeLog entry in this commit points to mount
issues for read-only mtab.

However, in all recent Linux distributions /etc/mtab is a symlink to
/proc/self/mounts and never writable. In fact, util-linux 2.39
(libmount) entirely removed support for a writable mtab.

At least since util-linux 2.19 (10-Feb-2011) /run/mount/utab is used
as replacement for userspace mount entries..

diff --git a/lib/mount.c b/lib/mount.c
index d71e6fc5571904039e9fc948c493bffc5cb8f74d..f98a8bb368c17d5d5b2a7403cbb14bd11cd458bf 100644 (file)
--- a/lib/mount.c
+++ b/lib/mount.c
@@ -209,6 +209,12 @@ static int fuse_mount_opt_proc(void *data, const char *arg, int key,
 
        case KEY_MTAB_OPT:
                return fuse_opt_add_opt(&mo->mtab_opts, arg);
+
+       /* Third party options like 'x-gvfs-notrash' */
+       case FUSE_OPT_KEY_OPT:
+               return (strncmp("x-", arg, 2) == 0) ?
+                       fuse_opt_add_opt(&mo->mtab_opts, arg) :
+                       1;
        }
 
        /* Pass through unknown options */

diff --git a/lib/mount_util.c b/lib/mount_util.c
index 8027a2e016005db6e19db87f6371b59e07bce000..dd3227686c5404b603f80291f4cd6fd30008bb24 100644 (file)
--- a/lib/mount_util.c
+++ b/lib/mount_util.c
@@ -54,7 +54,6 @@ static int mtab_needs_update(const char *mnt)
         * Skip mtab update if /etc/mtab:
         *
         *  - doesn't exist,
-        *  - is a symlink,
         *  - is on a read-only filesystem.
         */
        res = lstat(_PATH_MOUNTED, &stbuf);
@@ -65,9 +64,6 @@ static int mtab_needs_update(const char *mnt)
                uid_t ruid;
                int err;
 
-               if (S_ISLNK(stbuf.st_mode))
-                       return 0;
-
                ruid = getuid();
                if (ruid != 0)
                        setreuid(0, -1);

diff --git a/util/fusermount.c b/util/fusermount.c
index a2dd8e1202cb7e1b142eeba2a1adc6757090f0ed..fe75631ef53ae7118c0cfd035e329bf7f55c7f63 100644 (file)
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -97,6 +97,30 @@ static struct mntent *GETMNTENT(FILE *stream)
 #define GETMNTENT getmntent
 #endif // GETMNTENT_NEEDS_UNESCAPING
 
+/*
+ * Take a ',' separated option string and extract "x-" options
+ */
+static void extract_x_options(const char *original, char *non_x_opts, char *x_opts)
+{
+       size_t len;
+       const char *opt, *opt_end;
+       char *opt_buf;
+
+       len = strlen(original);
+
+       for (opt = original; opt < original + len; opt = opt_end + 1) {
+               opt_end = strchr(opt, ',');
+               if (opt_end == NULL)
+                       opt_end = original + len;
+
+               opt_buf = strncmp(opt, "x-", 2) ? non_x_opts : x_opts;
+
+               if (strlen(opt_buf) > 1)
+                       strncat(opt_buf, ",", 2);
+
+               strncat(opt_buf, opt, opt_end - opt);
+       }
+}
 
 static const char *get_user_name(void)
 {
@@ -1135,6 +1159,11 @@ static int mount_fuse(const char *mnt, const char *opts, const char **type)
        char *mnt_opts = NULL;
        const char *real_mnt = mnt;
        int mountpoint_fd = -1;
+       size_t opts_size;
+       char *do_mount_opts;
+       char *x_opts;
+       size_t add_mount_opts_size, add_mount_opts_len;
+       char *add_mount_opts;
 
        fd = open_fuse_device(&dev);
        if (fd == -1)
@@ -1151,11 +1180,17 @@ static int mount_fuse(const char *mnt, const char *opts, const char **type)
                }
        }
 
+       // Extract any options starting with "x-"
+       opts_size = strlen(opts) + 1;
+       do_mount_opts = malloc(opts_size);
+       x_opts = malloc(opts_size);
+       extract_x_options(opts, do_mount_opts, x_opts);
+
        res = check_perm(&real_mnt, &stbuf, &mountpoint_fd);
        restore_privs();
        if (res != -1)
                res = do_mount(real_mnt, type, stbuf.st_mode & S_IFMT,
-                              fd, opts, dev, &source, &mnt_opts);
+                              fd, do_mount_opts, dev, &source, &mnt_opts);
 
        if (mountpoint_fd != -1)
                close(mountpoint_fd);
@@ -1170,7 +1205,18 @@ static int mount_fuse(const char *mnt, const char *opts, const char **type)
        }
 
        if (geteuid() == 0) {
-               res = add_mount(source, mnt, *type, mnt_opts);
+               // Add back the options starting with "x-" to opts from do_mount
+               add_mount_opts_size = strlen(mnt_opts) + strlen(x_opts) + 2;
+               add_mount_opts = malloc(add_mount_opts_size);
+
+               strncpy(add_mount_opts, mnt_opts, add_mount_opts_size - 1);
+               add_mount_opts_len = strlen(add_mount_opts);
+               if (add_mount_opts_len > 0)
+                       strncat(add_mount_opts, ",", 2);
+               strncat(add_mount_opts, x_opts,
+                       add_mount_opts_size - add_mount_opts_len - 2);
+
+               res = add_mount(source, mnt, *type, add_mount_opts);
                if (res == -1) {
                        /* Can't clean up mount in a non-racy way */
                        goto fail_close_fd;