linux-kernel - Re: [PATCH 1/2] slub: fix leakage

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]

Date:	Sat, 3 Nov 2007 18:27:58 +0100
From:	"Olivér Pintér" <oliver.pntr@...il.com>
To:	"Hugh Dickins" <hugh@...itas.com>
Cc:	"Christoph Lameter" <clameter@....com>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH 1/2] slub: fix leakage

Q: It's needed auch to 2.6.22-stable?

On 11/3/07, Hugh Dickins <hugh@...itas.com> wrote:
> Slub has been quite leaky under load.  Taking mm_struct as an example, in
> a loop of swapping kernel builds, after the first iteration slabinfo shows:
> Name        Objects Objsize    Space Slabs/Part/Cpu  O/S O %Fr %Ef Flg
> mm_struct        55     840    73.7K         18/7/4    4 0  38  62 A
> but Objects and Partials steadily creep up - after the 340th iteration:
> mm_struct       110     840   188.4K        46/36/4    4 0  78  49 A
>
> The culprit turns out to be __slab_alloc(), where it copes with the race
> that another task has assigned the cpu slab while we were allocating one.
> Don't rush off to load_freelist there: that assumes c->freelist is empty,
> and will lose all of its free slots when c->page->freelist is not empty.
> Instead just do a local allocation from c->freelist when it has one.
>
> Which fixes the leakage: Objects and Partials then remain stable.
>
> Signed-off-by: Hugh Dickins <hugh@...itas.com>
> ---
> I recommend this for 2.6.24-rc2 and 2.6.23-stable.
>
>  mm/slub.c |    5 +++++
>  1 file changed, 5 insertions(+)
>
> --- 2.6.24-rc1/mm/slub.c	2007-10-24 07:16:04.000000000 +0100
> +++ linux/mm/slub.c	2007-11-03 13:22:31.000000000 +0000
> @@ -1525,6 +1525,11 @@ new_slab:
>  				 * want the current one since its cache hot
>  				 */
>  				discard_slab(s, new);
> +				if (c->freelist) {
> +					object = c->freelist;
> +					c->freelist = object[c->offset];
> +					return object;
> +				}
>  				slab_lock(c->page);
>  				goto load_freelist;
>  			}
> -
> 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/
>


-- 
Thanks,
Oliver
-
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/