From 5f1b64e9a9b7ee9cfd32c6b2fab796e29bfed075 Mon Sep 17 00:00:00 2001 From: Adrian Huang Date: Wed, 13 Nov 2024 18:21:46 +0800 Subject: sched/numa: fix memory leak due to the overwritten vma->numab_state [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): [] __kmalloc_cache_noprof+0x2f9/0x3f0 [] task_numa_work+0x725/0xa00 [] task_work_run+0x58/0x90 [] syscall_exit_to_user_mode+0x1c8/0x1e0 [] do_syscall_64+0x85/0x150 [] 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 Reported-by: Jiwei Sun Reviewed-by: Raghavendra K T Reviewed-by: Vlastimil Babka Cc: Ben Segall Cc: Dietmar Eggemann Cc: Ingo Molnar Cc: Juri Lelli Cc: Mel Gorman Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Valentin Schneider Cc: Vincent Guittot Cc: Signed-off-by: Andrew Morton --- kernel/sched/fair.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fbdca89c677f..a59ae2e23daf 100644 --- a/kernel/sched/fair.c +++ b/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; -- cgit v1.2.3-70-g09d2