The patch titled
Subject: sched/numa: fix memory leak due to the overwritten vma->numab_state
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
sched-numa-fix-memory-leak-due-to-the-overwritten-vma-numab_state.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/sched-numa-fix-memory-leak-due-to-the-overwritten-vma-numab_state.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Adrian Huang <ahuang12@xxxxxxxxxx>
Subject: sched/numa: fix memory leak due to the overwritten vma->numab_state
Date: Wed, 13 Nov 2024 18:21:46 +0800
[Problem Description]
When running the hackbench program of LTP, the following memory leak is
reported by kmemleak.
# /opt/ltp/testcases/bin/hackbench 20 thread 1000
Running with 20*40 (== 800) tasks.
# dmesg | grep kmemleak
...
kmemleak: 480 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
kmemleak: 665 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff888cd8ca2c40 (size 64):
comm "hackbench", pid 17142, jiffies 4299780315
hex dump (first 32 bytes):
ac 74 49 00 01 00 00 00 4c 84 49 00 01 00 00 00 .tI.....L.I.....
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace (crc bff18fd4):
[<ffffffff81419a89>] __kmalloc_cache_noprof+0x2f9/0x3f0
[<ffffffff8113f715>] task_numa_work+0x725/0xa00
[<ffffffff8110f878>] task_work_run+0x58/0x90
[<ffffffff81ddd9f8>] syscall_exit_to_user_mode+0x1c8/0x1e0
[<ffffffff81dd78d5>] do_syscall_64+0x85/0x150
[<ffffffff81e0012b>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
...
This issue can be consistently reproduced on three different servers:
* a 448-core server
* a 256-core server
* a 192-core server
[Root Cause]
Since multiple threads are created by the hackbench program (along with
the command argument 'thread'), a shared vma might be accessed by two or
more cores simultaneously. When two or more cores observe that
vma->numab_state is NULL at the same time, vma->numab_state will be
overwritten.
Although current code ensures that only one thread scans the VMAs in a
single 'numa_scan_period', there might be a chance for another thread
to enter in the next 'numa_scan_period' while we have not gotten till
numab_state allocation [1].
Note that the command `/opt/ltp/testcases/bin/hackbench 50 process 1000`
cannot the reproduce the issue. It is verified with 200+ test runs.
[Solution]
Use the cmpxchg atomic operation to ensure that only one thread executes
the vma->numab_state assignment.
[1] https://lore.kernel.org/lkml/1794be3c-358c-4cdc-a43d-a1f841d91ef7@xxxxxxx/
Link: https://lkml.kernel.org/r/20241113102146.2384-1-ahuang12@xxxxxxxxxx
Fixes: ef6a22b70f6d ("sched/numa: apply the scan delay to every new vma")
Signed-off-by: Adrian Huang <ahuang12@xxxxxxxxxx>
Reported-by: Jiwei Sun <sunjw10@xxxxxxxxxx>
Reviewed-by: Raghavendra K T <raghavendra.kt@xxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/kernel/sched/fair.c~sched-numa-fix-memory-leak-due-to-the-overwritten-vma-numab_state
+++ a/kernel/sched/fair.c
@@ -3399,10 +3399,16 @@ retry_pids:
/* Initialise new per-VMA NUMAB state. */
if (!vma->numab_state) {
- vma->numab_state = kzalloc(sizeof(struct vma_numab_state),
- GFP_KERNEL);
- if (!vma->numab_state)
+ struct vma_numab_state *ptr;
+
+ ptr = kzalloc(sizeof(*ptr), GFP_KERNEL);
+ if (!ptr)
+ continue;
+
+ if (cmpxchg(&vma->numab_state, NULL, ptr)) {
+ kfree(ptr);
continue;
+ }
vma->numab_state->start_scan_seq = mm->numa_scan_seq;
_
Patches currently in -mm which might be from ahuang12@xxxxxxxxxx are
sched-numa-fix-memory-leak-due-to-the-overwritten-vma-numab_state.patch
