Re: [PATCH] userfaultfd: avoid the duplicated release for userfaultfd_ctx

["Xu, Yanfei" <yanfei.xu@xxxxxxxxxxxxx>]

ping Al Viro

Could you please help to review this patch? Thanks a lot.

Yanfei

On 7/15/20 12:12 AM, yanfei.xu@xxxxxxxxxxxxx wrote:
> From: Yanfei Xu <yanfei.xu@xxxxxxxxxxxxx>
>
> when get_unused_fd_flags gets failure, userfaultfd_ctx_cachep will
> be freed by userfaultfd_fops's release function which is the
> userfaultfd_release. So we could return directly after fput().
>
> userfaultfd_release()->userfaultfd_ctx_put(ctx)
>
> Fixes: d08ac70b1e0d (Wire UFFD up to SELinux)
> Reported-by: syzbot+75867c44841cb6373570@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Yanfei Xu <yanfei.xu@xxxxxxxxxxxxx>
> ---
>   fs/userfaultfd.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 3a4d6ac5a81a..e98317c15530 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -2049,7 +2049,7 @@ SYSCALL_DEFINE1(userfaultfd, int, flags)
>   	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
>   	if (fd < 0) {
>   		fput(file);
> -		goto out;
> +		return fd;
>   	}
>   
>   	ctx->owner = file_inode(file);