syzbot


KCSAN: data-race in flush_tlb_batched_pending / try_to_unmap_one
Status: fixed on 2022/03/08 16:11
Reported-by: syzbot+aa5bebed695edaccf0df@syzkaller.appspotmail.com
Fix commit: 5ee2fa2f0636 mm/rmap: fix potential batched TLB flush race
First crash: 190d, last: 135d

Sample crash report:
==================================================================
BUG: KCSAN: data-race in flush_tlb_batched_pending / try_to_unmap_one

write to 0xffff888105f713bc of 1 bytes by task 1803 on cpu 0:
 flush_tlb_batched_pending+0x5f/0x80 mm/rmap.c:691
 madvise_free_pte_range+0xee/0x7d0 mm/madvise.c:594
 walk_pmd_range mm/pagewalk.c:128 [inline]
 walk_pud_range mm/pagewalk.c:205 [inline]
 walk_p4d_range mm/pagewalk.c:240 [inline]
 walk_pgd_range mm/pagewalk.c:277 [inline]
 __walk_page_range+0x981/0x1160 mm/pagewalk.c:379
 walk_page_range+0x131/0x300 mm/pagewalk.c:475
 madvise_free_single_vma mm/madvise.c:734 [inline]
 madvise_dontneed_free mm/madvise.c:822 [inline]
 madvise_vma mm/madvise.c:996 [inline]
 do_madvise+0xe4a/0x1140 mm/madvise.c:1202
 __do_sys_madvise mm/madvise.c:1228 [inline]
 __se_sys_madvise mm/madvise.c:1226 [inline]
 __x64_sys_madvise+0x5d/0x70 mm/madvise.c:1226
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff888105f713bc of 1 bytes by task 69 on cpu 1:
 set_tlb_ubc_flush_pending mm/rmap.c:636 [inline]
 try_to_unmap_one+0x60e/0x1220 mm/rmap.c:1515
 rmap_walk_anon+0x2fb/0x470 mm/rmap.c:2301
 try_to_unmap+0xec/0x110
 shrink_page_list+0xe91/0x2620 mm/vmscan.c:1760
 shrink_inactive_list+0x3fb/0x730 mm/vmscan.c:2435
 shrink_list mm/vmscan.c:2662 [inline]
 shrink_lruvec+0x3c9/0x710 mm/vmscan.c:2981
 shrink_node_memcgs+0x23e/0x410 mm/vmscan.c:3170
 shrink_node+0x8f6/0x1190 mm/vmscan.c:3293
 kswapd_shrink_node mm/vmscan.c:4069 [inline]
 balance_pgdat+0x702/0xd30 mm/vmscan.c:4260
 kswapd+0x200/0x340 mm/vmscan.c:4520
 kthread+0x2c7/0x2e0 kernel/kthread.c:327
 ret_from_fork+0x1f/0x30

value changed: 0x01 -> 0x00

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 69 Comm: kswapd0 Not tainted 5.16.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (2):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-upstream-kcsan-gce 2022/01/12 07:56 upstream 6f38be8f2ccd 44d1319a .config log report info KCSAN: data-race in flush_tlb_batched_pending / try_to_unmap_one
ci2-upstream-kcsan-gce 2021/11/18 11:23 upstream 42eb8fdac2fc cafff8b6 .config log report info KCSAN: data-race in flush_tlb_batched_pending / try_to_unmap_one