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

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Message-ID: <CAB=NE6WdYcURTxNLngMk3+JQfNHG2MX1oE_Mv08G5zcw=mPOyw@mail.gmail.com>
Date:   Wed, 13 May 2020 08:19:25 -0600
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Al Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        Scott Branden <scott.branden@...adcom.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...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 Wed, May 13, 2020 at 7:13 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> On Wed, May 13, 2020 at 06:49:50AM +0100, Al Viro wrote:
> > On Tue, May 12, 2020 at 01:43:05PM -0600, Shuah Khan wrote:
> > > 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;
> >
> > Incidentally, why is that thing exported?
>
> Both kernel_read_file_from_fd() and kernel_read_file() are exported
> because they have users, however kernel_read_file() only has security
> stuff as a user. Do we want to get rid of the lsm hook for it?

Alright, yeah just the export needs to be removed. I have a patch
series dealing with these callers so will add it to my queue.

  Luis