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authorQian Cai <cai@lca.pw>2020-08-14 17:31:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-14 19:56:57 -0700
commita1f459354a0f011a7baf52e5f16cd9ca95f1e6f2 (patch)
tree242aecbed21ddc179b6b0a23158c07146b966411
parente0e3f42fd96cf830c61aa720f0abb4eef41c5ce3 (diff)
downloadlinux-stericsson-a1f459354a0f011a7baf52e5f16cd9ca95f1e6f2.tar.gz
mm/list_lru: fix a data race in list_lru_count_one
struct list_lru_one l.nr_items could be accessed concurrently as noticed by KCSAN, BUG: KCSAN: data-race in list_lru_count_one / list_lru_isolate_move write to 0xffffa102789c4510 of 8 bytes by task 823 on cpu 39: list_lru_isolate_move+0xf9/0x130 list_lru_isolate_move at mm/list_lru.c:180 inode_lru_isolate+0x12b/0x2a0 __list_lru_walk_one+0x122/0x3d0 list_lru_walk_one+0x75/0xa0 prune_icache_sb+0x8b/0xc0 super_cache_scan+0x1b8/0x250 do_shrink_slab+0x256/0x6d0 shrink_slab+0x41b/0x4a0 shrink_node+0x35c/0xd80 balance_pgdat+0x652/0xd90 kswapd+0x396/0x8d0 kthread+0x1e0/0x200 ret_from_fork+0x27/0x50 read to 0xffffa102789c4510 of 8 bytes by task 6345 on cpu 56: list_lru_count_one+0x116/0x2f0 list_lru_count_one at mm/list_lru.c:193 super_cache_count+0xe8/0x170 do_shrink_slab+0x95/0x6d0 shrink_slab+0x41b/0x4a0 shrink_node+0x35c/0xd80 do_try_to_free_pages+0x1f7/0xa10 try_to_free_pages+0x26c/0x5e0 __alloc_pages_slowpath+0x458/0x1290 __alloc_pages_nodemask+0x3bb/0x450 alloc_pages_vma+0x8a/0x2c0 do_anonymous_page+0x170/0x700 __handle_mm_fault+0xc9f/0xd00 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 Reported by Kernel Concurrency Sanitizer on: CPU: 56 PID: 6345 Comm: oom01 Tainted: G W L 5.5.0-next-20200205+ #4 Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 A shattered l.nr_items could affect the shrinker behaviour due to a data race. Fix it by adding READ_ONCE() for the read. Since the writes are aligned and up to word-size, assume those are safe from data races to avoid readability issues of writing WRITE_ONCE(var, var + val). Signed-off-by: Qian Cai <cai@lca.pw> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Marco Elver <elver@google.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Link: http://lkml.kernel.org/r/1581114679-5488-1-git-send-email-cai@lca.pw Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/list_lru.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/list_lru.c b/mm/list_lru.c
index e825804b3928..5aa6e44bc2ae 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -180,7 +180,7 @@ unsigned long list_lru_count_one(struct list_lru *lru,
rcu_read_lock();
l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg));
- count = l->nr_items;
+ count = READ_ONCE(l->nr_items);
rcu_read_unlock();
return count;