linux-kernel - Re: [PATCH v2 2/2] fs: avoid fdput() after failed fdget() in kernel_read_file_from

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Message-ID: <20200513054950.GT23230@ZenIV.linux.org.uk>
Date:   Wed, 13 May 2020 06:49:50 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     axboe@...nel.dk, zohar@...ux.vnet.ibm.com, mcgrof@...nel.org,
        keescook@...omium.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] fs: avoid fdput() after failed fdget() in
 kernel_read_file_from_fd()

On Tue, May 12, 2020 at 01:43:05PM -0600, Shuah Khan wrote:
> Fix kernel_read_file_from_fd() to avoid fdput() after a failed fdget().
> fdput() doesn't do fput() on this file since FDPUT_FPUT isn't set
> in fd.flags. Fix it anyway since failed fdget() doesn't require
> a fdput().
> 
> This was introduced in a commit that added kernel_read_file_from_fd() as
> a wrapper for the VFS common kernel_read_file().
> 
> Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()")
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> ---
>  fs/exec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index 06b4c550af5d..ea24bdce939d 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1021,8 +1021,8 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
>  		goto out;
>  
>  	ret = kernel_read_file(f.file, buf, size, max_size, id);
> -out:
>  	fdput(f);
> +out:
>  	return ret;

Again, that goto is a pointless obfuscation; just return -EBADF
and be done with that.

Incidentally, why is that thing exported?