linux-kernel - Re: [PATCH] x86/mm: fix use-after-free of ldt

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Date:   Thu, 24 Aug 2017 11:39:07 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Eric Biggers <ebiggers3@...il.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Christoph Hellwig <hch@....de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Thomas Gleixner <tglx@...utronix.de>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/mm: fix use-after-free of ldt_struct

Ingo,

 I'm assuming I get this through the -tip tree, which is where the
original commit 39a0526fb3f7 ("x86/mm: Factor out LDT init from
context init") came from.

                    Linus

On Thu, Aug 24, 2017 at 10:59 AM, Dave Hansen
<dave.hansen@...ux.intel.com> wrote:
> On 08/24/2017 10:50 AM, Eric Biggers wrote:
>> --- a/arch/x86/include/asm/mmu_context.h
>> +++ b/arch/x86/include/asm/mmu_context.h
>> @@ -148,9 +148,7 @@ static inline int init_new_context(struct task_struct *tsk,
>>               mm->context.execute_only_pkey = -1;
>>       }
>>       #endif
>> -     init_new_context_ldt(tsk, mm);
>> -
>> -     return 0;
>> +     return init_new_context_ldt(tsk, mm);
>>  }
>
> Sheesh.  That was silly.  Thanks for finding and fixing this!  Feel free
> to add my ack on it.