linux-kernel - Re: [x86/uaccess] 5b710f34e1: kernel BUG at mm/usercopy.c:75!

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Message-ID: <CA+55aFz_Y-BcWs4rW_SkX1a0unnwjU6dzrwZogetB9_vc7ZsFQ@mail.gmail.com>
Date:	Wed, 17 Aug 2016 14:52:15 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Rik van Riel <riel@...hat.com>,
	kernel test robot <xiaolong.ye@...el.com>, LKP <lkp@...org>,
	LKML <linux-kernel@...r.kernel.org>,
	Valdis Kletnieks <valdis.kletnieks@...edu>
Subject: Re: [x86/uaccess] 5b710f34e1: kernel BUG at mm/usercopy.c:75!

On Wed, Aug 17, 2016 at 2:45 PM, Kees Cook <keescook@...omium.org> wrote:
>
> But PageSlab(page) should trip, returning __check_heap_object, which
> for SLOB should just return NULL, skipping all the rest of the
> checks...

SLOB doesn't actually set that for all allocations.

See "slob_alloc_node()", for example. It just returns a multi-order allocation.

(See also kfree(), which uses PageSlab() to determine it it should do
slob_free() or just free the pages directly).

         Linus