From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:46088 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751157AbdAQKNb (ORCPT ); Tue, 17 Jan 2017 05:13:31 -0500 Subject: Patch "mm/slab.c: fix SLAB freelist randomization duplicate entries" has been added to the 4.9-stable tree To: jsperbeck@google.com, akpm@linux-foundation.org, cl@linux.com, gregkh@linuxfoundation.org, iamjoonsoo.kim@lge.com, penberg@kernel.org, rientjes@google.com, thgarnie@google.com, torvalds@linux-foundation.org Cc: , From: Date: Tue, 17 Jan 2017 11:02:39 +0100 Message-ID: <148464735916490@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm/slab.c: fix SLAB freelist randomization duplicate entries to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-slab.c-fix-slab-freelist-randomization-duplicate-entries.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From c4e490cf148e85ead0d1b1c2caaba833f1d5b29f Mon Sep 17 00:00:00 2001 From: John Sperbeck Date: Tue, 10 Jan 2017 16:58:24 -0800 Subject: mm/slab.c: fix SLAB freelist randomization duplicate entries From: John Sperbeck commit c4e490cf148e85ead0d1b1c2caaba833f1d5b29f upstream. This patch fixes a bug in the freelist randomization code. When a high random number is used, the freelist will contain duplicate entries. It will result in different allocations sharing the same chunk. It will result in odd behaviours and crashes. It should be uncommon but it depends on the machines. We saw it happening more often on some machines (every few hours of running tests). Fixes: c7ce4f60ac19 ("mm: SLAB freelist randomization") Link: http://lkml.kernel.org/r/20170103181908.143178-1-thgarnie@google.com Signed-off-by: John Sperbeck Signed-off-by: Thomas Garnier Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/slab.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/mm/slab.c +++ b/mm/slab.c @@ -2475,7 +2475,6 @@ union freelist_init_state { unsigned int pos; unsigned int *list; unsigned int count; - unsigned int rand; }; struct rnd_state rnd_state; }; @@ -2501,8 +2500,7 @@ static bool freelist_state_initialize(un } else { state->list = cachep->random_seq; state->count = count; - state->pos = 0; - state->rand = rand; + state->pos = rand % count; ret = true; } return ret; @@ -2511,7 +2509,9 @@ static bool freelist_state_initialize(un /* Get the next entry on the list and randomize it using a random shift */ static freelist_idx_t next_random_slot(union freelist_init_state *state) { - return (state->list[state->pos++] + state->rand) % state->count; + if (state->pos >= state->count) + state->pos = 0; + return state->list[state->pos++]; } /* Swap two freelist entries */ Patches currently in stable-queue which might be from jsperbeck@google.com are queue-4.9/mm-slab.c-fix-slab-freelist-randomization-duplicate-entries.patch