linux-kernel - Re: [PATCH] userfaultfd: avoid the duplicated release for userfaultfd

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Date:   Sun, 19 Jul 2020 21:58:34 +0800
From:   "Xu, Yanfei" <yanfei.xu@...driver.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] userfaultfd: avoid the duplicated release for
 userfaultfd_ctx

ping Al Viro

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

Yanfei

On 7/15/20 12:12 AM, yanfei.xu@...driver.com wrote:
> From: Yanfei Xu <yanfei.xu@...driver.com>
> 
> 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@...kaller.appspotmail.com
> Signed-off-by: Yanfei Xu <yanfei.xu@...driver.com>
> ---
>   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);
>