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From:   Eric Dumazet <edumazet@google.com>
Date:   Sat, 15 Aug 2020 10:38:58 -0700
Message-ID: <CANn89i+YhDW2HRPNvfuHSDtrqGgXstgzTgcOx=A40XwJwbhSmg@mail.gmail.com>
Subject: Re: [PATCH] x86/fsgsbase/64: Fix NULL deref in 86_fsgsbase_read_task
To:     Ingo Molnar <mingo@kernel.org>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Jann Horn <jannh@google.com>,
        syzbot <syzkaller@googlegroups.com>,
        Andy Lutomirski <luto@kernel.org>,
        "Chang S . Bae" <chang.seok.bae@intel.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Markus T Metzger <markus.t.metzger@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ravi Shankar <ravi.v.shankar@intel.com>,
        Rik van Riel <riel@surriel.com>,
        Thomas Gleixner <tglx@linutronix.de>
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On Sat, Aug 15, 2020 at 4:48 AM Ingo Molnar <mingo@kernel.org> wrote:
>
>
> * Eric Dumazet <edumazet@google.com> wrote:
>
> > syzbot found its way in 86_fsgsbase_read_task() [1]
> >
> > Fix is to make sure ldt pointer is not NULL.
>
> Thanks for this fix. Linus has picked it up (inclusive the typos to
> the x86_fsgsbase_read_task() function name ;-), it's now upstream
> under:
>
>   8ab49526b53d: ("x86/fsgsbase/64: Fix NULL deref in 86_fsgsbase_read_task")
>
> By the fixes tag it looks like this should probably be backported all
> the way back to ~v4.20 or so?

This is absolutely right, sorry about the lack of a stable tag.

Most of my patches usually land into David Miller trees, where the
stable tag is not welcomed.
We use  Fixes: tags to convey the exact information needed for stable backports.

Thanks.