fs: ubifs: Fix memleak and double free in u-boot wrapper functions

When mounting ubifs e.g. through command 'ubifsmount' one global static
superblock 'ubifs_sb' is used _and_ the requested volume is opened (like
in Linux).  The pointer returned by 'ubifs_open_volume()' is stored in
that superblock struct and freed later on cmd 'ubifsumount' or another
call to 'ubifsmount' with a different volume, through ubifs_umount() and
ubi_close_volume().

In ubifs_ls(), ubifs_exists(), ubifs_size(), and ubifs_read() the volume
was opened again, which is technically no problem with regard to
refcounting, but here the still valid pointer in sb was overwritten,
leading to a memory leak.  Even worse, when using one of those
functions and calling ubifsumount later, ubi_close_volume() was called
again but now on an already freed pointer, leading to a double free.
This actually crashed with different invalid memory accesses on a board
using the old distro boot and a rather long script handling RAUC
updates.

Example:

    > ubi part UBI
    > ubifsmount ubi0:boot
    > test -e ubi ubi0:boot /boot.scr.uimg
    > ubifsumount

The ubifs specific commands 'ubifsls' and 'ubifsload' check for a
mounted volume by themselves, for the generic fs variants 'ls', 'load',
(and 'size', and 'test -e') this is covered by special ubifs handling in
fs_set_blk_dev() and deeper down blk_get_device_part_str() then.  So for
ubifs_ls(), ubifs_exists(), ubifs_size(), and ubifs_read() we can be
sure the volume is opened and the necessary struct pointer in sb is
valid, so it is not needed to open volume again.

Fixes: 9eefe2a2b37 ("UBIFS: Implement read-only UBIFS support in U-Boot")
Fixes: 29cc5bcadfc ("ubifs: Add functions for generic fs use")
Signed-off-by: Alexander Dahl <ada@thorsis.com>

diff --git a/fs/ubifs/ubifs.c b/fs/ubifs/ubifs.c
index 048730db7ff74c7a844abe6bdb705971e36f51cd..61ae5580e6215378c03fc137fcfd44af89bf7760 100644 (file)
--- a/fs/ubifs/ubifs.c
+++ b/fs/ubifs/ubifs.c
@@ -614,7 +614,6 @@ int ubifs_set_blk_dev(struct blk_desc *rbdd, struct disk_partition *info)
 
 int ubifs_ls(const char *filename)
 {
-       struct ubifs_info *c = ubifs_sb->s_fs_info;
        struct file *file;
        struct dentry *dentry;
        struct inode *dir;
@@ -622,7 +621,6 @@ int ubifs_ls(const char *filename)
        unsigned long inum;
        int ret = 0;
 
-       c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READONLY);
        inum = ubifs_findfile(ubifs_sb, (char *)filename);
        if (!inum) {
                ret = -1;
@@ -656,31 +654,24 @@ out_mem:
                free(dir);
 
 out:
-       ubi_close_volume(c->ubi);
        return ret;
 }
 
 int ubifs_exists(const char *filename)
 {
-       struct ubifs_info *c = ubifs_sb->s_fs_info;
        unsigned long inum;
 
-       c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READONLY);
        inum = ubifs_findfile(ubifs_sb, (char *)filename);
-       ubi_close_volume(c->ubi);
 
        return inum != 0;
 }
 
 int ubifs_size(const char *filename, loff_t *size)
 {
-       struct ubifs_info *c = ubifs_sb->s_fs_info;
        unsigned long inum;
        struct inode *inode;
        int err = 0;
 
-       c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READONLY);
-
        inum = ubifs_findfile(ubifs_sb, (char *)filename);
        if (!inum) {
                err = -1;
@@ -698,7 +689,6 @@ int ubifs_size(const char *filename, loff_t *size)
 
        ubifs_iput(inode);
 out:
-       ubi_close_volume(c->ubi);
        return err;
 }
 
@@ -893,7 +883,6 @@ int ubifs_read(const char *filename, void *buf, loff_t offset,
                return -1;
        }
 
-       c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READONLY);
        /* ubifs_findfile will resolve symlinks, so we know that we get
         * the real file here */
        inum = ubifs_findfile(ubifs_sb, (char *)filename);
@@ -957,7 +946,6 @@ put_inode:
        ubifs_iput(inode);
 
 out:
-       ubi_close_volume(c->ubi);
        return err;
 }