From: Kees Cook <keescook@chromium.org>
To: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Pekka Enberg <penberg@kernel.org>,
Christoph Lameter <cl@linux.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: Odd-sized kmem_cache_alloc and slub_debug=Z
Date: Fri, 7 Aug 2020 10:16:26 -0700 [thread overview]
Message-ID: <202008071010.69B612E@keescook> (raw)
In-Reply-To: <20200807160627.GA1420741@elver.google.com>
On Fri, Aug 07, 2020 at 06:06:27PM +0200, Marco Elver wrote:
> I found that the below debug-code using kmem_cache_alloc(), when using
> slub_debug=Z, results in the following crash:
>
> general protection fault, probably for non-canonical address 0xcccccca41caea170: 0000 [#1] PREEMPT SMP PTI
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.8.0+ #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014
> RIP: 0010:freelist_dereference mm/slub.c:272 [inline]
> RIP: 0010:get_freepointer mm/slub.c:278 [inline]
That really looks like more fun from my moving the freelist pointer...
> R13: cccccca41caea160 R14: ffffe7c6a072ba80 R15: ffffa3a41c96d540
Except that it's all cccc at the start, which doesn't look like "data"
nor the hardened freelist obfuscation.
> FS: 0000000000000000(0000) GS:ffffa3a41fc00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffa3a051c01000 CR3: 000000045140a001 CR4: 0000000000770ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 00000000
> Call Trace:
> ___slab_alloc+0x336/0x340 mm/slub.c:2690
> __slab_alloc mm/slub.c:2714 [inline]
> slab_alloc_node mm/slub.c:2788 [inline]
> slab_alloc mm/slub.c:2832 [inline]
> kmem_cache_alloc+0x135/0x200 mm/slub.c:2837
> start_kernel+0x3d6/0x44e init/main.c:1049
> secondary_startup_64+0xb6/0xc0 arch/x86/kernel/head_64.S:243
>
> Any ideas what might be wrong?
>
> This does not crash when redzones are not enabled.
>
> Thanks,
> -- Marco
>
> ------ >8 ------
>
> diff --git a/init/main.c b/init/main.c
> index 15bd0efff3df..f4aa5bb3f2ec 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1041,6 +1041,16 @@ asmlinkage __visible void __init start_kernel(void)
> sfi_init_late();
> kcsan_init();
>
> + /* DEBUG CODE */
> + {
> + struct kmem_cache *c = kmem_cache_create("test", 21, 1, 0, NULL);
> + char *buf;
> + BUG_ON(!c);
> + buf = kmem_cache_alloc(c, GFP_KERNEL);
> + kmem_cache_free(c, buf);
> + kmem_cache_destroy(c);
> + }
> +
> /* Do the rest non-__init'ed, we're now alive */
> arch_call_rest_init();
>
Which kernel version? Can you send your CONFIG too?
--
Kees Cook
next prev parent reply other threads:[~2020-08-07 17:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 16:06 Odd-sized kmem_cache_alloc and slub_debug=Z Marco Elver
2020-08-07 17:06 ` Pekka Enberg
2020-08-07 17:18 ` Marco Elver
2020-08-07 19:06 ` Pekka Enberg
2020-08-17 18:31 ` Marco Elver
2020-10-08 23:10 ` Kees Cook
2020-08-07 17:16 ` Kees Cook [this message]
2020-08-07 17:20 ` Marco Elver
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