Re: [syzbot] BUG: sleeping function called from invalid context in __munlock_pagevec

[Hugh Dickins <hughd@google.com>]

On Sat, 10 Jul 2021, syzbot wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ee268dee Add linux-next specific files for 20210707
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13ed30d2300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=59e1e3bbc3afca75
> dashboard link: https://syzkaller.appspot.com/bug?extid=cf9c548279bff83b0c97
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17a25ee4300000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f81928300000

I have checked with that C reproducer: this issue is in Linus's
current tree; but as expected, it is already fixed by
mm-rmap-fix-new-bug-premature-return-from-page_mlock_one.patch
in mmotm.

Hugh

> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+cf9c548279bff83b0c97@syzkaller.appspotmail.com
> 
> BUG: sleeping function called from invalid context at include/linux/pagemap.h:674
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 8467, name: syz-executor631
> 1 lock held by syz-executor631/8467:
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:359 [inline]
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: map_pte mm/page_vma_mapped.c:52 [inline]
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: page_vma_mapped_walk+0xd87/0x24f0 mm/page_vma_mapped.c:261
> Preemption disabled at:
> [<0000000000000000>] 0x0
> CPU: 0 PID: 8467 Comm: syz-executor631 Not tainted 5.13.0-next-20210707-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
>  ___might_sleep.cold+0x1f1/0x237 kernel/sched/core.c:9171
>  lock_page include/linux/pagemap.h:674 [inline]
>  __munlock_pagevec+0xa22/0x2340 mm/mlock.c:314
>  munlock_vma_pages_range+0x9d7/0xf00 mm/mlock.c:475
>  munlock_vma_pages_all mm/internal.h:354 [inline]
>  unlock_range mm/mmap.c:2811 [inline]
>  exit_mmap+0x47a/0x620 mm/mmap.c:3188
>  __mmput+0x122/0x470 kernel/fork.c:1152
>  mmput+0x58/0x60 kernel/fork.c:1173
>  exit_mm kernel/exit.c:501 [inline]
>  do_exit+0xae2/0x2a60 kernel/exit.c:812
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  __do_sys_exit_group kernel/exit.c:933 [inline]
>  __se_sys_exit_group kernel/exit.c:931 [inline]
>  __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x43e969
> Code: Unable to access opcode bytes at RIP 0x43e93f.
> RSP: 002b:00007ffce2d3a7a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 00000000004b02f0 RCX: 000000000043e969
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004b02f0
> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
> 
> =============================
> [ BUG: Invalid wait context ]
> 5.13.0-next-20210707-syzkaller #0 Tainted: G        W        
> -----------------------------
> syz-executor631/8467 is trying to lock:
> ffff888035ea6000 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: i_mmap_lock_read include/linux/fs.h:514 [inline]
> ffff888035ea6000 (&mapping->i_mmap_rwsem){++++}-{3:3}, at: rmap_walk_file+0x52f/0x710 mm/rmap.c:2337
> other info that might help us debug this:
> context-{4:4}
> 1 lock held by syz-executor631/8467:
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:359 [inline]
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: map_pte mm/page_vma_mapped.c:52 [inline]
>  #0: ffff8880343e0978 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: page_vma_mapped_walk+0xd87/0x24f0 mm/page_vma_mapped.c:261
> stack backtrace:
> CPU: 0 PID: 8467 Comm: syz-executor631 Tainted: G        W         5.13.0-next-20210707-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
>  print_lock_invalid_wait_context kernel/locking/lockdep.c:4666 [inline]
>  check_wait_context kernel/locking/lockdep.c:4727 [inline]
>  __lock_acquire.cold+0x213/0x3ab kernel/locking/lockdep.c:4965
>  lock_acquire kernel/locking/lockdep.c:5625 [inline]
>  lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
>  down_read+0x9a/0x440 kernel/locking/rwsem.c:1353
>  i_mmap_lock_read include/linux/fs.h:514 [inline]
>  rmap_walk_file+0x52f/0x710 mm/rmap.c:2337
>  rmap_walk+0x10d/0x190 mm/rmap.c:2366
>  page_mlock+0x448/0x650 mm/rmap.c:2029
>  __munlock_isolated_page+0x88/0x410 mm/mlock.c:122
>  __munlock_pagevec+0xd7f/0x2340 mm/mlock.c:322
>  munlock_vma_pages_range+0x9d7/0xf00 mm/mlock.c:475
>  munlock_vma_pages_all mm/internal.h:354 [inline]
>  unlock_range mm/mmap.c:2811 [inline]
>  exit_mmap+0x47a/0x620 mm/mmap.c:3188
>  __mmput+0x122/0x470 kernel/fork.c:1152
>  mmput+0x58/0x60 kernel/fork.c:1173
>  exit_mm kernel/exit.c:501 [inline]
>  do_exit+0xae2/0x2a60 kernel/exit.c:812
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  __do_sys_exit_group kernel/exit.c:933 [inline]
>  __se_sys_exit_group kernel/exit.c:931 [inline]
>  __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x43e969
> Code: Unable to access opcode bytes at RIP 0x43e93f.
> RSP: 002b:00007ffce2d3a7a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 00000000004b02f0 RCX: 000000000043e969
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004b02f0
> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
> 
> 
> ---
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> 
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