linux-kernel - Re: [PATCH] slab: fix the type of the index on freelist index accessor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAAG0J9-8WbO48jXpUfOq6CmHinL9dMg5Ee9-J9qndBEtZgWYJg@mail.gmail.com>
Date:	Thu, 24 Apr 2014 17:40:46 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	David Rientjes <rientjes@...gle.com>,
	Steven King <sfking@...dc.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] slab: fix the type of the index on freelist index accessor

On 18 April 2014 08:24, Joonsoo Kim <iamjoonsoo.kim@....com> wrote:
> commit 8dcc774 (slab: introduce byte sized index for the freelist of
> a slab) changes the size of freelist index and also changes prototype
> of accessor function to freelist index. And there was a mistake.
>
> The mistake is that although it changes the size of freelist index
> correctly, it changes the size of the index of freelist index incorrectly.
> With patch, freelist index can be 1 byte or 2 bytes, that means that
> num of object on on a slab can be more than 255. So we need more than 1
> byte for the index to find the index of free object on freelist. But,
> above patch makes this index type 1 byte, so slab which have more than
> 255 objects cannot work properly and in consequence of it, the system
> cannot boot.
>
> This issue was reported by Steven King on m68knommu which would use
> 2 bytes freelist index. Please refer following link.
>
> https://lkml.org/lkml/2014/4/16/433
>
> To fix it is so easy. To change the type of the index of freelist index
> on accessor functions is enough to fix this bug. Although 2 bytes is
> enough, I use 4 bytes since it have no bad effect and make things
> more easier. This fix was suggested and tested by Steven in his
> original report.
>
> Reported-by: Steven King <sfking@...dc.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

I also hit this problem on MIPS with v3.15-rc2 and 16K pages. With
this patch it boots fine.

Tested-by: James Hogan <james.hogan@...tec.com>

Thanks
James

> ---
> Hello, Pekka.
>
> Could you send this for v3.15-rc2?
> Without this patch, many architecture using 2 bytes freelist index cannot
> work properly, I guess.
>
> This patch is based on v3.15-rc1.
>
> Thanks.
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 388cb1a..d7f9f44 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -2572,13 +2572,13 @@ static void *alloc_slabmgmt(struct kmem_cache *cachep,
>         return freelist;
>  }
>
> -static inline freelist_idx_t get_free_obj(struct page *page, unsigned char idx)
> +static inline freelist_idx_t get_free_obj(struct page *page, unsigned int idx)
>  {
>         return ((freelist_idx_t *)page->freelist)[idx];
>  }
>
>  static inline void set_free_obj(struct page *page,
> -                                       unsigned char idx, freelist_idx_t val)
> +                                       unsigned int idx, freelist_idx_t val)
>  {
>         ((freelist_idx_t *)(page->freelist))[idx] = val;
>  }
> --
> 1.7.9.5
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/