From: Hugh Dickins <hughd@google.com> To: Chris Wright <chrisw@sous-sol.org> Cc: Andrea Righi <andrea@betterlinux.com>, CAI Qian <caiqian@redhat.com>, Andrea Arcangeli <aarcange@redhat.com>, Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH] ksm: fix race between ksmd and exiting task Date: Fri, 3 Jun 2011 09:37:13 -0700 (PDT) [thread overview] Message-ID: <alpine.LSU.2.00.1106030934130.1810@sister.anvils> (raw) In-Reply-To: <20110602173549.GL23047@sequoia.sous-sol.org> On Thu, 2 Jun 2011, Chris Wright wrote: > Andrea Righi reported a case where an exiting task can race against > ksmd. > > ksm_scan.mm_slot == the only registered mm > CPU 1 (bug program) CPU 2 (ksmd) > list_empty() is false > lock > ksm_scan.mm_slot > list_del > unlock > slot == &ksm_mm_head (but list is now empty_) > > Close this race by revalidating that the new slot is not simply the list > head again. Remarkably similar to my patch: it must be good! But yours appears to be more popular - thanks, Chris. > > Reported-by: Andrea Righi <andrea@betterlinux.com> > Cc: Hugh Dickins <hughd@google.com> Acked-by: Hugh Dickins <hughd@google.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Signed-off-by: Chris Wright <chrisw@sous-sol.org> Cc: stable@kernel.org > --- > mm/ksm.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 942dfc7..0373ce4 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -1301,6 +1301,9 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) > slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); > ksm_scan.mm_slot = slot; > spin_unlock(&ksm_mmlist_lock); > + /* We raced against exit of last slot on the list */ > + if (slot == &ksm_mm_head) > + return NULL; > next_mm: > ksm_scan.address = 0; > ksm_scan.rmap_list = &slot->rmap_list;
WARNING: multiple messages have this Message-ID (diff)
From: Hugh Dickins <hughd@google.com> To: Chris Wright <chrisw@sous-sol.org> Cc: Andrea Righi <andrea@betterlinux.com>, CAI Qian <caiqian@redhat.com>, Andrea Arcangeli <aarcange@redhat.com>, Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH] ksm: fix race between ksmd and exiting task Date: Fri, 3 Jun 2011 09:37:13 -0700 (PDT) [thread overview] Message-ID: <alpine.LSU.2.00.1106030934130.1810@sister.anvils> (raw) In-Reply-To: <20110602173549.GL23047@sequoia.sous-sol.org> On Thu, 2 Jun 2011, Chris Wright wrote: > Andrea Righi reported a case where an exiting task can race against > ksmd. > > ksm_scan.mm_slot == the only registered mm > CPU 1 (bug program) CPU 2 (ksmd) > list_empty() is false > lock > ksm_scan.mm_slot > list_del > unlock > slot == &ksm_mm_head (but list is now empty_) > > Close this race by revalidating that the new slot is not simply the list > head again. Remarkably similar to my patch: it must be good! But yours appears to be more popular - thanks, Chris. > > Reported-by: Andrea Righi <andrea@betterlinux.com> > Cc: Hugh Dickins <hughd@google.com> Acked-by: Hugh Dickins <hughd@google.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Signed-off-by: Chris Wright <chrisw@sous-sol.org> Cc: stable@kernel.org > --- > mm/ksm.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index 942dfc7..0373ce4 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -1301,6 +1301,9 @@ static struct rmap_item *scan_get_next_rmap_item(struct page **page) > slot = list_entry(slot->mm_list.next, struct mm_slot, mm_list); > ksm_scan.mm_slot = slot; > spin_unlock(&ksm_mmlist_lock); > + /* We raced against exit of last slot on the list */ > + if (slot == &ksm_mm_head) > + return NULL; > next_mm: > ksm_scan.address = 0; > ksm_scan.rmap_list = &slot->rmap_list; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-06-03 16:37 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-06-01 22:20 [BUG 3.0.0-rc1] ksm: NULL pointer dereference in ksm_do_scan() Andrea Righi 2011-06-01 22:20 ` Andrea Righi 2011-06-02 1:53 ` Chris Wright 2011-06-02 1:53 ` Chris Wright 2011-06-02 7:09 ` CAI Qian 2011-06-02 7:09 ` CAI Qian 2011-06-02 14:19 ` Andrea Righi 2011-06-02 14:19 ` Andrea Righi 2011-06-02 16:48 ` Chris Wright 2011-06-02 16:48 ` Chris Wright 2011-06-02 17:29 ` Hugh Dickins 2011-06-02 17:29 ` Hugh Dickins 2011-06-02 17:43 ` Andrea Arcangeli 2011-06-02 17:43 ` Andrea Arcangeli 2011-06-03 17:06 ` Hugh Dickins 2011-06-03 17:06 ` Hugh Dickins 2011-06-03 18:13 ` Andrea Arcangeli 2011-06-03 18:13 ` Andrea Arcangeli 2011-06-02 17:35 ` [PATCH] ksm: fix race between ksmd and exiting task Chris Wright 2011-06-02 17:35 ` Chris Wright 2011-06-02 20:12 ` Andrea Righi 2011-06-02 20:12 ` Andrea Righi 2011-06-02 21:23 ` Chris Wright 2011-06-02 21:23 ` Chris Wright 2011-06-03 16:37 ` Hugh Dickins [this message] 2011-06-03 16:37 ` Hugh Dickins 2011-06-04 0:54 ` [PATCH] ksm: fix NULL pointer dereference in scan_get_next_rmap_item Chris Wright 2011-06-04 0:54 ` Chris Wright 2011-06-02 20:10 ` [BUG 3.0.0-rc1] ksm: NULL pointer dereference in ksm_do_scan() Andrea Righi 2011-06-02 20:10 ` Andrea Righi 2011-06-03 4:42 ` CAI Qian 2011-06-03 4:42 ` CAI Qian 2011-06-02 14:31 ` Chris Wright 2011-06-02 14:31 ` Chris Wright 2011-06-02 14:36 ` Andrea Arcangeli 2011-06-02 14:36 ` Andrea Arcangeli 2011-06-02 15:36 ` Chris Wright 2011-06-02 15:36 ` Chris Wright 2011-06-02 16:44 ` Andrea Arcangeli 2011-06-02 16:44 ` Andrea Arcangeli 2011-06-02 20:15 ` Andrea Righi 2011-06-02 20:15 ` Andrea Righi 2011-06-02 21:35 ` Andrea Arcangeli 2011-06-02 21:35 ` Andrea Arcangeli 2011-06-03 4:50 ` CAI Qian 2011-06-03 4:50 ` CAI Qian 2011-06-03 4:44 ` CAI Qian 2011-06-03 4:44 ` CAI Qian
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