linux-kernel - Re: [PATCH v7 3/9] net/scm: Regularize compat handling of scm_detach

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Date:   Fri, 7 Aug 2020 13:29:24 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Sargun Dhillon <sargun@...gun.me>,
        Christian Brauner <christian@...uner.io>,
        Tycho Andersen <tycho@...ho.ws>,
        David Laight <David.Laight@...lab.com>,
        Christoph Hellwig <hch@....de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Aleksa Sarai <cyphar@...har.com>,
        Matt Denton <mpdenton@...gle.com>,
        Jann Horn <jannh@...gle.com>, Chris Palmer <palmer@...gle.com>,
        Robert Sesek <rsesek@...gle.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>, Shuah Khan <shuah@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Amit Pundir <amit.pundir@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v7 3/9] net/scm: Regularize compat handling of scm_detach_fds()

On Thu, Jul 9, 2020 at 11:28 AM Kees Cook <keescook@...omium.org> wrote:
>
> Duplicate the cleanups from commit 2618d530dd8b ("net/scm: cleanup
> scm_detach_fds") into the compat code.
>
> Replace open-coded __receive_sock() with a call to the helper.
>
> Move the check added in commit 1f466e1f15cf ("net: cleanly handle kernel
> vs user buffers for ->msg_control") to before the compat call, even
> though it should be impossible for an in-kernel call to also be compat.
>
> Correct the int "flags" argument to unsigned int to match fd_install()
> and similar APIs.
>
> Regularize any remaining differences, including a whitespace issue,
> a checkpatch warning, and add the check from commit 6900317f5eff ("net,
> scm: fix PaX detected msg_controllen overflow in scm_detach_fds") which
> fixed an overflow unique to 64-bit. To avoid confusion when comparing
> the compat handler to the native handler, just include the same check
> in the compat handler.
>
> Acked-by: Christian Brauner <christian.brauner@...ntu.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---

Hey Kees,
  So during the merge window (while chasing a few other regressions),
I noticed occasionally my Dragonboard 845c running AOSP having trouble
with the web browser crashing or other apps hanging, and I've bisected
the issue down to this change.

Unfortunately it doesn't revert cleanly so I can't validate reverting
it sorts things against linus/HEAD.  Anyway, I wanted to check and see
if you had any other reports of similar or any ideas what might be
going wrong?

thanks
-john