[PATCH] ubifs: Fix reference count leak in ubifsumount

Pali Rohár
2022-05-23T21:37:02Z

Original ubifs code was designed that after ubifs_umount() call it is
required to also call ubi_close_volume() which closes underlying UBI
volume. But U-Boot ubifs modification have not implemented it properly
which caused that ubifsumount command contains resource leak. It can be
observed by calling simple sequence of commands:

=> ubi part mtd2
ubi0: attaching mtd2
...
=> ubifsmount ubi0
=> ubifsumount
Unmounting UBIFS volume rootfs!
=> ubi detach
ubi0 error: ubi_detach_mtd_dev: ubi0 reference count 1, destroy anyway
ubi0: detaching mtd2
ubi0: mtd2 is detached

Fix this issue by calling ubi_close_volume() and mutex_unlock() in
directly in ubifs_umount() function before freeing U-Boot's global
ubifs_sb. And remove duplicate calls of these two functions in remaining
places. With this change ubifsumount command does not throw that error
anymore.

=> ubi part rootfs
ubi0: attaching mtd2
...
=> ubifsmount ubi0
=> ubifsumount
Unmounting UBIFS volume rootfs!
=> ubi detach
ubi0: detaching mtd2
ubi0: mtd2 is detached

Signed-off-by: Pali Rohár <pali@kernel.org>
---
fs/ubifs/super.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index e3a4c0bca270..7677dcc2a140 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1757,6 +1757,8 @@ void ubifs_umount(struct ubifs_info *c)
kfree(c->bottom_up_buf);
ubifs_debugging_exit(c);
#ifdef __UBOOT__
+ ubi_close_volume(c->ubi);
+ mutex_unlock(&c->umount_mutex);
/* Finally free U-Boot's global copy of superblock */
if (ubifs_sb != NULL) {
free(ubifs_sb->s_fs_info);
@@ -2058,9 +2060,9 @@ static void ubifs_put_super(struct super_block *sb)
ubifs_umount(c);
#ifndef __UBOOT__
bdi_destroy(&c->bdi);
-#endif
ubi_close_volume(c->ubi);
mutex_unlock(&c->umount_mutex);
+#endif
}
#endif

@@ -2328,13 +2330,13 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
out_umount:
ubifs_umount(c);
out_unlock:
- mutex_unlock(&c->umount_mutex);
#ifndef __UBOOT__
+ mutex_unlock(&c->umount_mutex);
out_bdi:
bdi_destroy(&c->bdi);
out_close:
-#endif
ubi_close_volume(c->ubi);
+#endif
out:
return err;
}
--
2.20.1