1 files changed, 20 insertions, 1 deletions

diff --git a/util-linux/mount.c b/util-linux/mount.c
index f0245f714..6bb18524d 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -1887,6 +1887,7 @@ static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
 // NB: mp->xxx fields may be trashed on exit
 static int singlemount(struct mntent *mp, int ignore_busy)
 {
+        int loopfd = -1;
         int rc = -1;
         unsigned long vfsflags;
         char *loopFile = NULL, *filteropts = NULL;
@@ -2026,7 +2027,20 @@ static int singlemount(struct mntent *mp, int ignore_busy)
                 if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
                         loopFile = bb_simplify_path(mp->mnt_fsname);
                         mp->mnt_fsname = NULL; // will receive malloced loop dev name
-                        if (set_loop(&mp->mnt_fsname, loopFile, 0, /*ro:*/ (vfsflags & MS_RDONLY)) < 0) {
+
+                        // mount always creates AUTOCLEARed loopdevs, so that umounting
+                        // drops them without any code in the userspace.
+                        // This happens since circa linux-2.6.25:
+                        // commit 96c5865559cee0f9cbc5173f3c949f6ce3525581
+                        // Date:    Wed Feb 6 01:36:27 2008 -0800
+                        // Subject: Allow auto-destruction of loop devices
+                        loopfd = set_loop(&mp->mnt_fsname,
+                                        loopFile,
+                                        0,
+                                        ((vfsflags & MS_RDONLY) ? BB_LO_FLAGS_READ_ONLY : 0)
+                                                | BB_LO_FLAGS_AUTOCLEAR
+                        );
+                        if (loopfd < 0) {
                                 if (errno == EPERM || errno == EACCES)
                                         bb_error_msg(bb_msg_perm_denied_are_you_root);
                                 else
@@ -2074,6 +2088,8 @@ static int singlemount(struct mntent *mp, int ignore_busy)
         }
 
         // If mount failed, clean up loop file (if any).
+        // (Newer kernels which support LO_FLAGS_AUTOCLEAR should not need this,
+        // merely "close(loopfd)" should do it?)
         if (ENABLE_FEATURE_MOUNT_LOOP && rc && loopFile) {
                 del_loop(mp->mnt_fsname);
                 if (ENABLE_FEATURE_CLEAN_UP) {
@@ -2086,6 +2102,9 @@ static int singlemount(struct mntent *mp, int ignore_busy)
         if (ENABLE_FEATURE_CLEAN_UP)
                 free(filteropts);
 
+        if (loopfd >= 0)
+                close(loopfd);
+
         if (errno == EBUSY && ignore_busy)
                 return 0;
         if (errno == ENOENT && (vfsflags & MOUNT_NOFAIL))