linux-kernel - Re: BUG: KASAN: use-after-free in cmp_ex

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Date:   Thu, 30 Nov 2017 09:27:30 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Meyer <thomas@...3r.de>
Cc:     Fengguang Wu <fengguang.wu@...el.com>, mingo@...hat.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, lkp@...org
Subject: Re: BUG: KASAN: use-after-free in cmp_ex_search+0x29/0x71

On Thu, Nov 30, 2017 at 06:16:58AM +0100, Thomas Meyer wrote:
> On Thu, Nov 30, 2017 at 11:36:06AM +0800, Fengguang Wu wrote:


> > [   40.847825] ==================================================================
> > [   40.848720] BUG: KASAN: use-after-free in cmp_ex_search+0x29/0x71:
> > 						ex_to_insn at lib/extable.c:23
> > 						 (inlined by) cmp_ex_search at lib/extable.c:104

Right after this it does:

> [   40.872223] kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
> [   40.873011] BUG: unable to handle kernel paging request at fffffbfff0766694
> [   40.874648] IP: 0xfffffbfff0766694
> [   40.875112] PGD 1b3df067 P4D 1b3df067 PUD 1b3de067 PMD 800000001ac001e3
> [   40.876293] Thread overran stack, or stack corrupted

which seems to suggest the machine is completely fucked and the uaf
could very well be the result of that.