• Qian Cai's avatar
    mm/list_lru: fix a data race in list_lru_count_one · a1f45935
    Qian Cai authored
    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: default avatarQian Cai <cai@lca.pw>
    Signed-off-by: default avatarAndrew 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.pwSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    a1f45935
list_lru.c 14.4 KB