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From: Andrea Arcangeli <aarcange@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Dmitry Vyukov <dvyukov@google.com>,
	syzbot 
	<bot+6a5269ce759a7bb12754ed9622076dc93f65a1f6@syzkaller.appspotmail.com>,
	Jan Beulich <JBeulich@suse.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	ldufour@linux.vnet.ibm.com, LKML <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	syzkaller-bugs@googlegroups.com,
	Thomas Gleixner <tglx@linutronix.de>,
	the arch/x86 maintainers <x86@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Hugh Dickins <hughd@google.com>,
	David Rientjes <rientjes@google.com>,
	linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thorsten Leemhuis <regressions@leemhuis.info>
Subject: Re: KASAN: use-after-free Read in __do_page_fault
Date: Tue, 31 Oct 2017 20:15:06 +0100	[thread overview]
Message-ID: <20171031191506.GB2799@redhat.com> (raw)
In-Reply-To: <fbf1e43d-1f73-09c1-1837-3600bcedd5d2@suse.cz>

On Tue, Oct 31, 2017 at 03:28:26PM +0100, Vlastimil Babka wrote:
> Hmm that could indeed work, Dmitry can you try the patch below?
> But it still seems rather fragile so I'd hope Andrea can do it more
> robust, or at least make sure that we don't reintroduce this kind of
> problem in the future (explicitly set vma to NULL with a comment?).

Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>

> 
> ----8<----
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index e2baeaa053a5..9bd16fc621db 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1441,6 +1441,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
>  	 * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
>  	 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
>  	 */
> +	pkey = vma_pkey(vma);
>  	fault = handle_mm_fault(vma, address, flags);
>  	major |= fault & VM_FAULT_MAJOR;
>  
> @@ -1467,7 +1468,6 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
>  		return;
>  	}
>  
> -	pkey = vma_pkey(vma);
>  	up_read(&mm->mmap_sem);
>  	if (unlikely(fault & VM_FAULT_ERROR)) {
>  		mm_fault_error(regs, error_code, address, &pkey, fault);
> 

  reply	other threads:[~2017-10-31 19:15 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-30 19:12 syzbot
2017-10-30 19:15 ` Dmitry Vyukov
2017-10-31 12:00   ` Vlastimil Babka
2017-10-31 12:42     ` Dmitry Vyukov
2017-10-31 13:20       ` Vlastimil Babka
2017-10-31 13:57         ` Vlastimil Babka
2017-10-31 14:11           ` Kirill A. Shutemov
2017-10-31 14:28             ` Vlastimil Babka
2017-10-31 19:15               ` Andrea Arcangeli [this message]
2017-11-01  7:42                 ` Vlastimil Babka
2017-11-01 10:17                   ` Andrea Arcangeli
2017-11-01 12:14                     ` Vlastimil Babka
2017-10-31 15:37           ` Linus Torvalds
2017-10-31 19:13             ` Andrea Arcangeli
2017-11-01 15:26               ` Linus Torvalds
2017-11-02 19:36                 ` Andrea Arcangeli
2017-11-02 10:00           ` Laurent Dufour

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