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author | Kefeng Wang <wangkefeng.wang@huawei.com> | 2022-08-27 19:19:59 +0800 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2022-09-11 20:26:04 -0700 |
commit | b4a0215e11dcfe23a48c65c6d6c82c0c2c551a48 (patch) | |
tree | ca0dc9fe6b7e331e2db88204fb44ad268f1b025d /mm | |
parent | 639118d1571f70b1157b4bb5ac574b0ab0f38099 (diff) | |
download | linux-b4a0215e11dcfe23a48c65c6d6c82c0c2c551a48.tar.gz |
mm: fix null-ptr-deref in kswapd_is_running()
kswapd_run/stop() will set pgdat->kswapd to NULL, which could race with kswapd_is_running() in kcompactd(), kswapd_run/stop() kcompactd() kswapd_is_running() pgdat->kswapd // error or nomal ptr verify pgdat->kswapd // load non-NULL pgdat->kswapd pgdat->kswapd = NULL task_is_running(pgdat->kswapd) // Null pointer derefence KASAN reports the null-ptr-deref shown below, vmscan: Failed to start kswapd on node 0 ... BUG: KASAN: null-ptr-deref in kcompactd+0x440/0x504 Read of size 8 at addr 0000000000000024 by task kcompactd0/37 CPU: 0 PID: 37 Comm: kcompactd0 Kdump: loaded Tainted: G OE 5.10.60 #1 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: dump_backtrace+0x0/0x394 show_stack+0x34/0x4c dump_stack+0x158/0x1e4 __kasan_report+0x138/0x140 kasan_report+0x44/0xdc __asan_load8+0x94/0xd0 kcompactd+0x440/0x504 kthread+0x1a4/0x1f0 ret_from_fork+0x10/0x18 At present kswapd/kcompactd_run() and kswapd/kcompactd_stop() are protected by mem_hotplug_begin/done(), but without kcompactd(). There is no need to involve memory hotplug lock in kcompactd(), so let's add a new mutex to protect pgdat->kswapd accesses. Also, because the kcompactd task will check the state of kswapd task, it's better to call kcompactd_stop() before kswapd_stop() to reduce lock conflicts. [akpm@linux-foundation.org: add comments] Link: https://lkml.kernel.org/r/20220827111959.186838-1-wangkefeng.wang@huawei.com Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: David Hildenbrand <david@redhat.com> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/compaction.c | 14 | ||||
-rw-r--r-- | mm/memory_hotplug.c | 2 | ||||
-rw-r--r-- | mm/page_alloc.c | 1 | ||||
-rw-r--r-- | mm/vmscan.c | 27 |
4 files changed, 31 insertions, 13 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 640fa76228dd..262c4676b32c 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1981,9 +1981,21 @@ static inline bool is_via_compact_memory(int order) return order == -1; } +/* + * Determine whether kswapd is (or recently was!) running on this node. + * + * pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't + * zero it. + */ static bool kswapd_is_running(pg_data_t *pgdat) { - return pgdat->kswapd && task_is_running(pgdat->kswapd); + bool running; + + pgdat_kswapd_lock(pgdat); + running = pgdat->kswapd && task_is_running(pgdat->kswapd); + pgdat_kswapd_unlock(pgdat); + + return running; } /* diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index dc727aee4ad3..9ae1f98548b1 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1940,8 +1940,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages, node_states_clear_node(node, &arg); if (arg.status_change_nid >= 0) { - kswapd_stop(node); kcompactd_stop(node); + kswapd_stop(node); } writeback_set_ratelimit(); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1d4278115d71..09386b81e68e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7616,6 +7616,7 @@ static void __meminit pgdat_init_internals(struct pglist_data *pgdat) int i; pgdat_resize_init(pgdat); + pgdat_kswapd_lock_init(pgdat); pgdat_init_split_queue(pgdat); pgdat_init_kcompactd(pgdat); diff --git a/mm/vmscan.c b/mm/vmscan.c index bb993b21953d..02e720c83901 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -4643,16 +4643,17 @@ void kswapd_run(int nid) { pg_data_t *pgdat = NODE_DATA(nid); - if (pgdat->kswapd) - return; - - pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); - if (IS_ERR(pgdat->kswapd)) { - /* failure at boot is fatal */ - BUG_ON(system_state < SYSTEM_RUNNING); - pr_err("Failed to start kswapd on node %d\n", nid); - pgdat->kswapd = NULL; + pgdat_kswapd_lock(pgdat); + if (!pgdat->kswapd) { + pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); + if (IS_ERR(pgdat->kswapd)) { + /* failure at boot is fatal */ + BUG_ON(system_state < SYSTEM_RUNNING); + pr_err("Failed to start kswapd on node %d\n", nid); + pgdat->kswapd = NULL; + } } + pgdat_kswapd_unlock(pgdat); } /* @@ -4661,12 +4662,16 @@ void kswapd_run(int nid) */ void kswapd_stop(int nid) { - struct task_struct *kswapd = NODE_DATA(nid)->kswapd; + pg_data_t *pgdat = NODE_DATA(nid); + struct task_struct *kswapd; + pgdat_kswapd_lock(pgdat); + kswapd = pgdat->kswapd; if (kswapd) { kthread_stop(kswapd); - NODE_DATA(nid)->kswapd = NULL; + pgdat->kswapd = NULL; } + pgdat_kswapd_unlock(pgdat); } static int __init kswapd_init(void) |