* [RESEND PATCH v3] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
@ 2021-09-06 3:46 yanghui
2021-09-06 3:53 ` Muchun Song
0 siblings, 1 reply; 2+ messages in thread
From: yanghui @ 2021-09-06 3:46 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, songmuchun, yanghui
Servers happened below panic:
Kernel version:5.4.56
BUG: unable to handle page fault for address: 0000000000002c48
RIP: 0010:__next_zones_zonelist+0x1d/0x40
[264003.977696] RAX: 0000000000002c40 RBX: 0000000000100dca RCX: 0000000000000014
[264003.977872] Call Trace:
[264003.977888] __alloc_pages_nodemask+0x277/0x310
[264003.977908] alloc_page_interleave+0x13/0x70
[264003.977926] handle_mm_fault+0xf99/0x1390
[264003.977951] __do_page_fault+0x288/0x500
[264003.977979] ? schedule+0x39/0xa0
[264003.977994] do_page_fault+0x30/0x110
[264003.978010] page_fault+0x3e/0x50
The reason of panic is that MAX_NUMNODES is passd in the third parameter
in function __alloc_pages_nodemask(preferred_nid). So if to access
zonelist->zoneref->zone_idx in __next_zones_zonelist the panic will happen.
In offset_il_node(), first_node() return nid from pol->v.nodes, after
this other threads may changed pol->v.nodes before next_node().
This race condition will let next_node return MAX_NUMNODES.So put
pol->nodes in a local variable.
The race condition is between offset_il_node and cpuset_change_task_nodemask:
CPU0: CPU1:
alloc_pages_vma()
interleave_nid(pol,)
offset_il_node(pol,)
first_node(pol->v.nodes) cpuset_change_task_nodemask
//nodes==0xc mpol_rebind_task
mpol_rebind_policy
mpol_rebind_nodemask(pol,nodes)
//nodes==0x3
next_node(nid, pol->v.nodes)//return MAX_NUMNODES
Signed-off-by: yanghui <yanghui.def@bytedance.com>
---
Changes in v2:
1.Fix WRITE_ONCE/READ_ONCE can't deal with more than sizeof(long) bits data.
Changes in v3:
1.Modify some wrong comments.
mm/mempolicy.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index e32360e90274..54f6eaff18c5 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1965,17 +1965,26 @@ unsigned int mempolicy_slab_node(void)
*/
static unsigned offset_il_node(struct mempolicy *pol, unsigned long n)
{
- unsigned nnodes = nodes_weight(pol->nodes);
- unsigned target;
+ nodemask_t nodemask = pol->nodes;
+ unsigned int target, nnodes;
int i;
int nid;
+ /*
+ * The barrier will stabilize the nodemask in a register or on
+ * the stack so that it will stop changing under the code.
+ *
+ * Between first_node() and next_node(), pol->nodes could be changed
+ * by other threads. So we put pol->nodes in a local stack.
+ */
+ barrier();
+ nnodes = nodes_weight(nodemask);
if (!nnodes)
return numa_node_id();
target = (unsigned int)n % nnodes;
- nid = first_node(pol->nodes);
+ nid = first_node(nodemask);
for (i = 0; i < target; i++)
- nid = next_node(nid, pol->nodes);
+ nid = next_node(nid, nodemask);
return nid;
}
--
2.20.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [RESEND PATCH v3] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
2021-09-06 3:46 [RESEND PATCH v3] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task yanghui
@ 2021-09-06 3:53 ` Muchun Song
0 siblings, 0 replies; 2+ messages in thread
From: Muchun Song @ 2021-09-06 3:53 UTC (permalink / raw)
To: yanghui; +Cc: Andrew Morton, Linux Memory Management List, LKML
On Mon, Sep 6, 2021 at 11:47 AM yanghui <yanghui.def@bytedance.com> wrote:
>
> Servers happened below panic:
> Kernel version:5.4.56
> BUG: unable to handle page fault for address: 0000000000002c48
> RIP: 0010:__next_zones_zonelist+0x1d/0x40
> [264003.977696] RAX: 0000000000002c40 RBX: 0000000000100dca RCX: 0000000000000014
> [264003.977872] Call Trace:
> [264003.977888] __alloc_pages_nodemask+0x277/0x310
> [264003.977908] alloc_page_interleave+0x13/0x70
> [264003.977926] handle_mm_fault+0xf99/0x1390
> [264003.977951] __do_page_fault+0x288/0x500
> [264003.977979] ? schedule+0x39/0xa0
> [264003.977994] do_page_fault+0x30/0x110
> [264003.978010] page_fault+0x3e/0x50
>
> The reason of panic is that MAX_NUMNODES is passd in the third parameter
> in function __alloc_pages_nodemask(preferred_nid). So if to access
> zonelist->zoneref->zone_idx in __next_zones_zonelist the panic will happen.
>
> In offset_il_node(), first_node() return nid from pol->v.nodes, after
> this other threads may changed pol->v.nodes before next_node().
> This race condition will let next_node return MAX_NUMNODES.So put
> pol->nodes in a local variable.
>
> The race condition is between offset_il_node and cpuset_change_task_nodemask:
> CPU0: CPU1:
> alloc_pages_vma()
> interleave_nid(pol,)
> offset_il_node(pol,)
> first_node(pol->v.nodes) cpuset_change_task_nodemask
> //nodes==0xc mpol_rebind_task
> mpol_rebind_policy
> mpol_rebind_nodemask(pol,nodes)
> //nodes==0x3
> next_node(nid, pol->v.nodes)//return MAX_NUMNODES
>
> Signed-off-by: yanghui <yanghui.def@bytedance.com>
LGTM.
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2021-09-06 3:55 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-06 3:46 [RESEND PATCH v3] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task yanghui
2021-09-06 3:53 ` Muchun Song
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).