mount-tool: use libmount to parse /proc/self/mountinfo

Same motivation as in other places: let's use a single logic to parse this.

Use path_equal() to compare the path.

A bug in error handling is fixed: if we failed after the GREEDY_REALLOC but
before the line that sets the last item to NULL, we would jump to
_cleanup_strv_free_ with the strv unterminated. Let's use GREEDY_REALLOC0
to avoid the issue.

2 files changed, 30 insertions, 34 deletions

diff --git a/meson.build b/meson.build
index 15e3394b91..d24e8000e9 100644
--- a/meson.build
+++ b/meson.build
@@ -2470,6 +2470,7 @@ exe = executable('systemd-mount',
                  'src/mount/mount-tool.c',
                  include_directories : includes,
                  link_with : [libshared],
+                 dependencies: [libmount],
                  install_rpath : rootlibexecdir,
                  install : true)
 public_programs += exe
diff --git a/src/mount/mount-tool.c b/src/mount/mount-tool.c
index b290095b0e..fc18dd28d7 100644
--- a/src/mount/mount-tool.c
+++ b/src/mount/mount-tool.c
@@ -17,6 +17,7 @@
 #include "format-util.h"
 #include "fs-util.h"
 #include "fstab-util.h"
+#include "libmount-util.h"
 #include "main-func.h"
 #include "mount-util.h"
 #include "mountpoint-util.h"
@@ -713,9 +714,11 @@ static int start_transient_automount(
 }
 
 static int find_mount_points(const char *what, char ***list) {
-        _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
+        _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL;
+        _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL;
         _cleanup_strv_free_ char **l = NULL;
         size_t bufsize = 0, n = 0;
+        int r;
 
         assert(what);
         assert(list);
@@ -723,55 +726,47 @@ static int find_mount_points(const char *what, char ***list) {
         /* Returns all mount points obtained from /proc/self/mountinfo in *list,
          * and the number of mount points as return value. */
 
-        proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
-        if (!proc_self_mountinfo)
-                return log_error_errno(errno, "Can't open /proc/self/mountinfo: %m");
+        table = mnt_new_table();
+        iter = mnt_new_iter(MNT_ITER_FORWARD);
+        if (!table || !iter)
+                return log_oom();
 
-        for (;;) {
-                _cleanup_free_ char *path = NULL, *where = NULL, *dev = NULL;
-                int r;
+        r = mnt_table_parse_mtab(table, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse /proc/self/mountinfo: %m");
 
-                r = fscanf(proc_self_mountinfo,
-                           "%*s "       /* (1) mount id */
-                           "%*s "       /* (2) parent id */
-                           "%*s "       /* (3) major:minor */
-                           "%*s "       /* (4) root */
-                           "%ms "       /* (5) mount point */
-                           "%*s"        /* (6) mount options */
-                           "%*[^-]"     /* (7) optional fields */
-                           "- "         /* (8) separator */
-                           "%*s "       /* (9) file system type */
-                           "%ms"        /* (10) mount source */
-                           "%*s"        /* (11) mount options 2 */
-                           "%*[^\n]",   /* some rubbish at the end */
-                           &path, &dev);
-                if (r != 2) {
-                        if (r == EOF)
-                                break;
+        for (;;) {
+                struct libmnt_fs *fs;
+                const char *source, *target;
 
-                        continue;
-                }
+                r = mnt_table_next_fs(table, iter, &fs);
+                if (r == 1)
+                        break;
+                if (r < 0)
+                        return log_error_errno(r, "Failed to get next entry from /proc/self/mountinfo: %m");
 
-                if (!streq(what, dev))
+                source = mnt_fs_get_source(fs);
+                target = mnt_fs_get_target(fs);
+                if (!source || !target)
                         continue;
 
-                r = cunescape(path, UNESCAPE_RELAX, &where);
-                if (r < 0)
+                if (!path_equal(source, what))
                         continue;
 
                 /* one extra slot is needed for the terminating NULL */
-                if (!GREEDY_REALLOC(l, bufsize, n + 2))
+                if (!GREEDY_REALLOC0(l, bufsize, n + 2))
                         return log_oom();
 
-                l[n++] = TAKE_PTR(where);
+                l[n] = strdup(target);
+                if (!l[n])
+                        return log_oom();
+                n++;
         }
 
-        if (!GREEDY_REALLOC(l, bufsize, n + 1))
+        if (!GREEDY_REALLOC0(l, bufsize, n + 1))
                 return log_oom();
 
-        l[n] = NULL;
         *list = TAKE_PTR(l);
-
         return n;
 }