On Wed, Oct 28, 2020 at 11:03:52AM +0800, Zhiqiang Liu wrote:
>
> In create_pipe_files(), if alloc_file_clone() fails, we will call
> put_pipe_info to release pipe, and call fput() to release f.
> However, we donot call iput() to free inode.
Huh? Have you actually tried to trigger that failure exit?
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
> Signed-off-by: Feilong Lin <linfeilong@xxxxxxxxxx>
> ---
> fs/pipe.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 0ac197658a2d..8856607fde65 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -924,6 +924,7 @@ int create_pipe_files(struct file **res, int flags)
> if (IS_ERR(res[0])) {
> put_pipe_info(inode, inode->i_pipe);
> fput(f);
> + iput(inode);
> return PTR_ERR(res[0]);
No. That inode is created with refcount 1. If alloc_file_pseudo()
succeeds, the reference we'd been holding has been transferred into
dentry allocated by alloc_file_pseudo() (and attached to f).
>From that point on we do *NOT* own a reference to inode and no
subsequent failure exits have any business releasing it.
In particular, alloc_file_clone() DOES NOT create extra references
to inode, whether it succeeds or fails. Dropping the reference
to f will take care of everything.
If you tried to trigger that failure exit with your patch applied,
you would've seen double iput(), as soon as you return from sys_pipe()
to userland and task_work is processed (which is where the real
destructor of struct file will happen).
NAK.
