Hi,
Cc +Richard +David
On 2020/1/6 16:04, zhangyi (F) wrote:
> After commit 4fdcfab5b553 ("jffs2: fix use-after-free on symlink
> traversal"), it expose a freeing uninitialized memory problem due to
> this commit move the operaion of freeing f->target to
> jffs2_i_callback(), which may not be initialized in some error path of
> allocating jffs2 inode (eg: jffs2_iget()->iget_locked()->
> destroy_inode()->..->jffs2_i_callback()->kfree(f->target)).
>
Could you please elaborate the scenario in which the use of a uninitialized
f->target is possible ? IMO one case is that there are concurrent
jffs2_lookup() and jffs2 GC on an evicted inode, and two new inodes
are created, and then one needless inode is destroyed.
> Fix this by initialize the jffs2_inode_info just after allocating it.
>
> Reported-by: Guohua Zhong <zhongguoh...@huawei.com>
> Reported-by: Huaijie Yi <yihuai...@huawei.com>
> Signed-off-by: zhangyi (F) <yi.zh...@huawei.com>
> Cc: sta...@vger.kernel.org
> ---
A Fixes tag is also needed here.
> fs/jffs2/fs.c | 2 --
> fs/jffs2/super.c | 2 ++
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
> index ab8cdd9e9325..50a9df7d43a5 100644
> --- a/fs/jffs2/fs.c
> +++ b/fs/jffs2/fs.c
> @@ -270,7 +270,6 @@ struct inode *jffs2_iget(struct super_block *sb, unsigned
> long ino)
> f = JFFS2_INODE_INFO(inode);
> c = JFFS2_SB_INFO(inode->i_sb);
>
> - jffs2_init_inode_info(f);
> mutex_lock(&f->sem);
>
> ret = jffs2_do_read_inode(c, f, inode->i_ino, &latest_node);
> @@ -438,7 +437,6 @@ struct inode *jffs2_new_inode (struct inode *dir_i,
> umode_t mode, struct jffs2_r
> return ERR_PTR(-ENOMEM);
>
> f = JFFS2_INODE_INFO(inode);
> - jffs2_init_inode_info(f);
> mutex_lock(&f->sem);
>
> memset(ri, 0, sizeof(*ri));
> diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
> index 0e6406c4f362..90373898587f 100644
> --- a/fs/jffs2/super.c
> +++ b/fs/jffs2/super.c
> @@ -42,6 +42,8 @@ static struct inode *jffs2_alloc_inode(struct super_block
> *sb)
> f = kmem_cache_alloc(jffs2_inode_cachep, GFP_KERNEL);
> if (!f)
> return NULL;
> +
> + jffs2_init_inode_info(f);
> return &f->vfs_inode;
> }
>
>
