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...

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@lenovo.com 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@amd.com/

Link: https://lkml.kernel.org/r/20241113102146.2384-1-ahuang12@lenovo.com Fixes: ef6a22b70f6d ("sched/numa: apply the scan delay to every new vma") Signed-off-by: Adrian Huang ahuang12@lenovo.com Reported-by: Jiwei Sun sunjw10@lenovo.com Reviewed-by: Raghavendra K T raghavendra.kt@amd.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Cc: Ben Segall bsegall@google.com Cc: Dietmar Eggemann dietmar.eggemann@arm.com Cc: Ingo Molnar mingo@redhat.com Cc: Juri Lelli juri.lelli@redhat.com Cc: Mel Gorman mgorman@suse.de Cc: Peter Zijlstra peterz@infradead.org Cc: Steven Rostedt rostedt@goodmis.org Cc: Valentin Schneider vschneid@redhat.com Cc: Vincent Guittot vincent.guittot@linaro.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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@lenovo.com are

sched-numa-fix-memory-leak-due-to-the-overwritten-vma-numab_state.patch