Re: [RFC PATCH v4 5/5] btrfs: ioctl: don't free iov when -EAGAIN in uring encoded read

[Pavel Begunkov <asml.silence@gmail.com>]

On 3/17/25 13:57, Sidong Yang wrote:
> This patch fixes a bug on encoded_read. In btrfs_uring_encoded_read(),
> btrfs_encoded_read could return -EAGAIN when receiving requests concurrently.
> And data->iov goes to out_free and it freed and return -EAGAIN. io-uring
> subsystem would call it again and it doesn't reset data. And data->iov
> freed and iov_iter reference it. iov_iter would be used in
> btrfs_uring_read_finished() and could be raise memory bug.

Fixes should go first. Please send it separately, and CC Mark.
A "Fixes" tag would also be good to have.

> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
>   fs/btrfs/ioctl.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index a7b52fd99059..02fa8dd1a3ce 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4922,6 +4922,9 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
>   
>   	ret = btrfs_encoded_read(&kiocb, &data->iter, &data->args, &cached_state,
>   				 &disk_bytenr, &disk_io_size);
> +
> +	if (ret == -EAGAIN)
> +		goto out_acct;
>   	if (ret < 0 && ret != -EIOCBQUEUED)
>   		goto out_free;
>   

-- 
Pavel Begunkov