Btrfs: Make free_ipath() deal gracefully with NULL pointers
authorJesper Juhl <jj@chaosbits.net>
Thu, 12 Apr 2012 20:47:52 +0000 (22:47 +0200)
committerDavid Sterba <dsterba@suse.cz>
Wed, 18 Apr 2012 17:22:20 +0000 (19:22 +0200)
commit4735fb282830c0966b301dabcccf4753fa6604bb
tree1749491d41f888c29dbad6de37fe3fbe81a38fc3
parentcdc6a3952558f00b1bc3b6401e1cf98797632fe2
Btrfs: Make free_ipath() deal gracefully with NULL pointers

Make free_ipath() behave like most other freeing functions in the
kernel and gracefully do nothing when passed a NULL pointer.

Besides this making the bahaviour consistent with functions such as
kfree(), vfree(), btrfs_free_path() etc etc, it also fixes a real NULL
deref issue in fs/btrfs/ioctl.c::btrfs_ioctl_ino_to_path(). In that
function we have this code:

...
        ipath = init_ipath(size, root, path);
        if (IS_ERR(ipath)) {
                ret = PTR_ERR(ipath);
                ipath = NULL;
                goto out;
        }
...
out:
        btrfs_free_path(path);
        free_ipath(ipath);
...

If we ever take the true branch of that 'if' statement we'll end up
passing a NULL pointer to free_ipath() which will subsequently
dereference it and we'll go "Boom" :-(
This patch will avoid that.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
fs/btrfs/backref.c