[syzbot] BUG: soft lockup in do_wp_page (4)

[Dmitry Vyukov]

On Thu, Mar 18, 2021 at 8:31 PM syzbot
<syzbot+0b036374a865ba0efa8e at syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    bf152b0b Merge tag 'for_linus' of git://git.kernel.org/pub..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17d5264ed00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2c9917c41f0bc04b
> dashboard link: https://syzkaller.appspot.com/bug?extid=0b036374a865ba0efa8e
> 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+0b036374a865ba0efa8e at syzkaller.appspotmail.com
>
> watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:3684]

+Will, arm

If I am reading this commit correctly, this is caused by:

commit cae118b6acc309539b33339e846cbb19187c164c
Author: Will Deacon
Date:   Wed Mar 3 13:49:27 2021 +0000
    arm64: Drop support for CMDLINE_EXTEND

syzbot passes lots of critical things in CONFIG_CMDLINE:
https://github.com/google/syzkaller/blob/c3c81c94865791469d376eba84f4a2d7763d3f71/dashboard/config/linux/upstream-arm64-kasan.config#L495
but also wants the bootloader args to be appended.
What is the way to do it now?




> Modules linked in:
> irq event stamp: 10067468
> hardirqs last  enabled at (10067467): [<ffff8000143de478>] exit_to_kernel_mode+0x38/0x230 arch/arm64/kernel/entry-common.c:59
> hardirqs last disabled at (10067468): [<ffff8000143deb40>] enter_el1_irq_or_nmi+0x10/0x20 arch/arm64/kernel/entry-common.c:101
> softirqs last  enabled at (10067362): [<ffff8000100109e0>] _stext+0x9e0/0x1084
> softirqs last disabled at (10067297): [<ffff80001015976c>] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline]
> softirqs last disabled at (10067297): [<ffff80001015976c>] invoke_softirq kernel/softirq.c:228 [inline]
> softirqs last disabled at (10067297): [<ffff80001015976c>] __irq_exit_rcu+0x46c/0x510 kernel/softirq.c:422
> CPU: 0 PID: 3684 Comm: syz-executor.1 Not tainted 5.12.0-rc3-syzkaller-00036-gbf152b0b41dc #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:1212
> sp : ffff00000c6cf4a0
> x29: ffff00000c6cf4a0 x28: fffffc0000180b00
> x27: ffff00007fc13ec0 x26: ffff00000b709458
> x25: ffff6000016e128b x24: 0000000000001458
> x23: ffff00000b708000 x22: fffffc0000180b40
> x21: ffff8000154e2938 x20: dfff800000000000
> x19: fffffc0000180b00 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000
> x15: 0000000000000000 x14: 1fffe000018d9e5e
> x13: 0000000000000001 x12: ffff7f8000030167
> x11: 1fffff8000030166 x10: ffff7f8000030166
> x9 : 0000000000000000 x8 : ffff600000c05a00
> x7 : 0000000000000000 x6 : 000000000000003f
> x5 : 0000000000000040 x4 : 1ffff00002fa5748
> x3 : 1fffe000016e1001 x2 : 0000000000000004
> x1 : 0000000000000040 x0 : ffff00000602ce00
> Call trace:
>  clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:21
>  post_alloc_hook+0x130/0x1fc mm/page_alloc.c:2305
>  prep_new_page mm/page_alloc.c:2311 [inline]
>  get_page_from_freelist+0x2024/0x2a40 mm/page_alloc.c:3951
>  __alloc_pages_nodemask+0x2a0/0x24dc mm/page_alloc.c:5001
>  alloc_pages_vma+0xb4/0x510 mm/mempolicy.c:2240
>  wp_page_copy+0x198/0x16e0 mm/memory.c:2853
>  do_wp_page+0x1d8/0xbbc mm/memory.c:3160
>  handle_pte_fault mm/memory.c:4336 [inline]
>  __handle_mm_fault+0x1020/0x21d4 mm/memory.c:4453
>  handle_mm_fault+0x1cc/0x4dc mm/memory.c:4551
>  __do_page_fault arch/arm64/mm/fault.c:507 [inline]
>  do_page_fault+0x228/0x880 arch/arm64/mm/fault.c:591
>  do_mem_abort+0x64/0x1c0 arch/arm64/mm/fault.c:805
>  el0_da+0x3c/0x50 arch/arm64/kernel/entry-common.c:308
>  el0_sync_handler+0x168/0x1b0 arch/arm64/kernel/entry-common.c:435
>  el0_sync+0x170/0x180 arch/arm64/kernel/entry.S:699
>
>
> ---
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