On 06.09.21 19:33, Andrew Morton wrote:
(cc's added)
On Sun, 05 Sep 2021 18:05:40 -0700 syzbot <syzbot+aa7a876b8108f1622bc3@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
Hello,
syzbot found the following issue on:
HEAD commit: 49624efa65ac Merge tag 'denywrite-for-5.15' of git://githu..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12eff4b3300000
kernel config: https://syzkaller.appspot.com/x/.config?x=c598149362d97396
dashboard link: https://syzkaller.appspot.com/bug?extid=aa7a876b8108f1622bc3
compiler: aarch64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
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+aa7a876b8108f1622bc3@xxxxxxxxxxxxxxxxxxxxxxxxx
watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:26449]
Modules linked in:
irq event stamp: 248
hardirqs last enabled at (247): [<ffff8000145ed108>] __exit_to_kernel_mode arch/arm64/kernel/entry-common.c:81 [inline]
hardirqs last enabled at (247): [<ffff8000145ed108>] exit_to_kernel_mode+0x38/0x230 arch/arm64/kernel/entry-common.c:91
hardirqs last disabled at (248): [<ffff8000145ed0c0>] enter_el1_irq_or_nmi+0x10/0x20 arch/arm64/kernel/entry-common.c:227
softirqs last enabled at (182): [<ffff800010010964>] _stext+0x964/0xff8
softirqs last disabled at (41): [<ffff800010160f58>] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline]
softirqs last disabled at (41): [<ffff800010160f58>] invoke_softirq kernel/softirq.c:439 [inline]
softirqs last disabled at (41): [<ffff800010160f58>] __irq_exit_rcu+0x208/0x4f0 kernel/softirq.c:636
CPU: 0 PID: 26449 Comm: syz-executor.1 Not tainted 5.14.0-syzkaller-09416-g49624efa65ac #0
Hardware name: linux,dummy-virt (DT)
pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:23
lr : clear_highpage include/linux/highmem.h:181 [inline]
lr : kernel_init_free_pages.part.0+0x6c/0x17c mm/page_alloc.c:1286
sp : ffff800019be75e0
x29: ffff800019be75e0 x28: 0000000000000000 x27: 0000000000000000
x26: ffff000009d64940 x25: ffff6000013ac928 x24: 00000000000014c0
x23: ffff000009d63480 x22: fffffc0000173340 x21: ffff800015794a78
x20: dfff800000000000 x19: fffffc0000173300 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 1ffff0000337ce86 x13: 0000000000000013 x12: ffff7f800002e667
x11: 1fffff800002e666 x10: ffff7f800002e666 x9 : 0000000000000000
x8 : ffff600000b99a00 x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 1ffff00003060d98 x3 : 1fffe000013ac691
x2 : 0000000000000004 x1 : 0000000000000040 x0 : ffff000005ccc880
Call trace:
clear_page+0x14/0x28 arch/arm64/lib/clear_page.S:21
kernel_init_free_pages mm/page_alloc.c:1283 [inline]
post_alloc_hook+0x1ac/0x25c mm/page_alloc.c:2426
prep_new_page mm/page_alloc.c:2436 [inline]
get_page_from_freelist+0x184c/0x2320 mm/page_alloc.c:4168
__alloc_pages+0x1a8/0x21d0 mm/page_alloc.c:5390
alloc_pages_vma+0xbc/0x530 mm/mempolicy.c:2252
alloc_zeroed_user_highpage_movable+0x9c/0xd0 arch/arm64/mm/fault.c:926
do_anonymous_page mm/memory.c:3767 [inline]
handle_pte_fault mm/memory.c:4556 [inline]
__handle_mm_fault+0xbc4/0x2210 mm/memory.c:4693
handle_mm_fault+0x1dc/0x4f0 mm/memory.c:4791
__do_page_fault arch/arm64/mm/fault.c:499 [inline]
do_page_fault+0x230/0x8c0 arch/arm64/mm/fault.c:599
do_translation_fault+0x1a4/0x210 arch/arm64/mm/fault.c:680
do_mem_abort+0x64/0x1c0 arch/arm64/mm/fault.c:813
el0_da+0x7c/0x2b0 arch/arm64/kernel/entry-common.c:481
el0t_64_sync_handler+0x168/0x1b0 arch/arm64/kernel/entry-common.c:616
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:572
At first sight, looks unrelated. Being stuck in clear_page() is weird;
we're running inside a VM ("dummy-virt"), whereby such stuck tasks in
the guests are sometimes the result of the hypervisor being stuck (e.g.,
heavily overcommitted).
If we don't get a reproducer, that's most probably the root cause. Let's
see.
--
Thanks,
David / dhildenb
