From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, linux-mm@kvack.org,
mm-commits@vger.kernel.org, songmuchun@bytedance.com,
stable@vger.kernel.org, torvalds@linux-foundation.org,
yanghui.def@bytedance.com
Subject: [patch 7/8] mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
Date: Wed, 08 Sep 2021 18:10:20 -0700 [thread overview]
Message-ID: <20210909011020.5uPjbdM2T%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210908180859.d523d4bb4ad8eec11c61500d@linux-foundation.org>
From: yanghui <yanghui.def@bytedance.com>
Subject: mm/mempolicy: fix a race between offset_il_node and mpol_rebind_task
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 for the panic is that MAX_NUMNODES is passed in the third
parameter in __alloc_pages_nodemask(preferred_nid). So access to
zonelist->zoneref->zone_idx in __next_zones_zonelist will cause a panic.
In offset_il_node(), first_node() returns nid from pol->v.nodes, after
this other threads may chang 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
Link: https://lkml.kernel.org/r/20210906034658.48721-1-yanghui.def@bytedance.com
Signed-off-by: yanghui <yanghui.def@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/mempolicy.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
--- a/mm/mempolicy.c~mm-mempolicy-fix-a-race-between-offset_il_node-and-mpol_rebind_task
+++ a/mm/mempolicy.c
@@ -1876,17 +1876,26 @@ 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;
}
_
next prev parent reply other threads:[~2021-09-09 1:10 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-09 1:08 incoming Andrew Morton
2021-09-09 1:10 ` [patch 1/8] mm/hmm: bypass devmap pte when all pfn requested flags are fulfilled Andrew Morton
2021-09-09 1:10 ` [patch 2/8] mm/hugetlb: initialize hugetlb_usage in mm_init Andrew Morton
2021-09-09 1:10 ` [patch 3/8] mm,vmscan: fix divide by zero in get_scan_count Andrew Morton
2021-09-09 1:10 ` [patch 4/8] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype Andrew Morton
2021-09-09 1:10 ` [patch 5/8] mmap_lock: change trace and locking order Andrew Morton
2021-09-09 12:56 ` Liam Howlett
2021-09-09 1:10 ` [patch 6/8] mm/kmemleak: allow __GFP_NOLOCKDEP passed to kmemleak's gfp Andrew Morton
2021-09-09 1:10 ` Andrew Morton [this message]
2021-09-09 1:10 ` [patch 8/8] nds32/setup: remove unused memblock_region variable in setup_memory() Andrew Morton
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