Re: [syzbot] BUG: soft lockup in handle_mm_fault

[Dmitry Vyukov]

On Tue, May 18, 2021 at 9:53 PM syzbot
<syzbot+44b5132ce1d2d712a574@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    d07f6ca9 Linux 5.13-rc2
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1772d265d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d2302c3f03979672
> dashboard link: https://syzkaller.appspot.com/bug?extid=44b5132ce1d2d712a574
> userspace arch: arm64
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+44b5132ce1d2d712a574@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:13795]

This is the issue with arm64 not using CONFIG_CMDLINE, the timeout
should be 10x larger.

#syz dup: BUG: soft lockup in do_wp_page (4)

> Modules linked in:
> irq event stamp: 2262
> hardirqs last  enabled at (2261): [<ffff8000144b1da8>] exit_to_kernel_mode+0x38/0x230 arch/arm64/kernel/entry-common.c:63
> hardirqs last disabled at (2262): [<ffff8000144b2470>] enter_el1_irq_or_nmi+0x10/0x20 arch/arm64/kernel/entry-common.c:105
> softirqs last  enabled at (2200): [<ffff8000100109e0>] _stext+0x9e0/0x1084
> softirqs last disabled at (2117): [<ffff80001015e8d4>] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline]
> softirqs last disabled at (2117): [<ffff80001015e8d4>] invoke_softirq kernel/softirq.c:440 [inline]
> softirqs last disabled at (2117): [<ffff80001015e8d4>] __irq_exit_rcu+0x494/0x550 kernel/softirq.c:637
> CPU: 0 PID: 13795 Comm: syz-executor.1 Not tainted 5.13.0-rc2-syzkaller #0
> Hardware name: linux,dummy-virt (DT)
> pstate: 00000005 (nzcv daif -PAN -UAO -TCO BTYPE=--)
> pc : clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:23
> lr : clear_highpage include/linux/highmem.h:203 [inline]
> lr : kernel_init_free_pages+0x74/0x180 mm/page_alloc.c:1238
> sp : ffff8000199874c0
> x29: ffff8000199874c0 x28: ffff00007fc13ec0 x27: 0000000000000000
> x26: ffff00000b47af00 x25: ffff60000168f5e0 x24: 00000000000014c0
> x23: ffff00000b479a40 x22: fffffc0000185bc0 x21: ffff80001560e558
> x20: dfff800000000000 x19: fffffc0000185b80 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> x14: 1ffff00003330e62 x13: 0000000000000001 x12: ffff7f8000030b77
> x11: 1fffff8000030b76 x10: ffff7f8000030b76 x9 : 0000000000000000
> x8 : ffff600000c2de00 x7 : 0000000000000000 x6 : 000000000000003f
> x5 : 0000000000000040 x4 : 1ffff000030ec350 x3 : 1fffe0000168f349
> x2 : 0000000000000004 x1 : 0000000000000040 x0 : ffff00000616ef40
> Call trace:
>  clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:21
>  post_alloc_hook+0x108/0x21c mm/page_alloc.c:2350
>  prep_new_page mm/page_alloc.c:2358 [inline]
>  get_page_from_freelist+0x1998/0x235c mm/page_alloc.c:3994
>  __alloc_pages+0x1a8/0x21e0 mm/page_alloc.c:5200
>  alloc_pages_vma+0xb4/0x510 mm/mempolicy.c:2236
>  wp_page_copy+0x198/0x1720 mm/memory.c:2896
>  do_wp_page+0x1d8/0xbbc mm/memory.c:3203
>  handle_pte_fault mm/memory.c:4385 [inline]
>  __handle_mm_fault+0x10c8/0x26f0 mm/memory.c:4502
>  handle_mm_fault+0x1cc/0x4e0 mm/memory.c:4600
>  __do_page_fault arch/arm64/mm/fault.c:507 [inline]
>  do_page_fault+0x230/0x8c0 arch/arm64/mm/fault.c:607
>  do_mem_abort+0x64/0x1c0 arch/arm64/mm/fault.c:821
>  el0_da+0x3c/0x50 arch/arm64/kernel/entry-common.c:306
>  el0_sync_handler+0x168/0x1b0 arch/arm64/kernel/entry-common.c:427
>  el0_sync+0x198/0x1c0 arch/arm64/kernel/entry.S:734
>
>
> ---
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