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

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Message-ID: <43bcad51-b210-c1fa-c729-471fe008ba61@linux.intel.com>
Date:   Thu, 24 Aug 2017 10:59:18 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Eric Biggers <ebiggers3@...il.com>, x86@...nel.org
Cc:     linux-mm@...ck.org, 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>,
        Linus Torvalds <torvalds@...ux-foundation.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@...r.kernel.org
Subject: Re: [PATCH] x86/mm: fix use-after-free of ldt_struct

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.