BUG: unable to handle kernel NULL pointer dereference in try_async_pf

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11761525100000
kernel config: https://syzkaller.appspot.com/x/.config?x=be4578b3f1083656
dashboard link: https://syzkaller.appspot.com/bug?extid=9ed140de7b79fa93497b
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
CC: [b...@alien8.de h...@zytor.com jmat...@google.com jo...@8bytes.org k...@vger.kernel.org linux-...@vger.kernel.org mi...@redhat.com pbon...@redhat.com sean.j.chr...@intel.com tg...@linutronix.de vkuz...@redhat.com wanp...@tencent.com x...@kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9ed140...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 8de20067 P4D 8de20067 PUD 956e0067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 18796 Comm: syz-executor.3 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:252 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x60 kernel/kcov.c:202
Code: c2 00 01 ff 00 74 11 f7 c2 00 01 00 00 74 35 83 b9 04 14 00 00 00 74 2c 8b 91 e0 13 00 00 83 fa 02 75 21 48 8b 91 e8 13 00 00 <48> 8b 32 48 8d 7e 01 8b 89 e4 13 00 00 48 39 cf 73 08 48 89 44 f2
RSP: 0018:ffffc90017377758 EFLAGS: 00010246
RAX: ffffffff8119026b RBX: 0000000000000000 RCX: ffff888087f36300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900173778a7 R08: ffffffff811901af R09: ffffc900173778a7
R10: ffffed1013de8882 R11: 0000000000000000 R12: ffff88809f298580
R13: 1ffff92002e6ef13 R14: dffffc0000000000 R15: ffffc90017377898
FS: 00007f24a3aef700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000092cb6000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
try_async_pf+0x1db/0x5a0 arch/x86/kvm/mmu/mmu.c:4078
direct_page_fault+0xbf6/0x1c50 arch/x86/kvm/mmu/mmu.c:4124
kvm_mmu_do_page_fault arch/x86/kvm/mmu.h:115 [inline]
kvm_mmu_page_fault+0x13d/0xde0 arch/x86/kvm/mmu/mmu.c:5422
vcpu_enter_guest+0x6666/0x89a0 arch/x86/kvm/x86.c:8604
vcpu_run+0x352/0xcd0 arch/x86/kvm/x86.c:8669
kvm_arch_vcpu_ioctl_run+0x451/0x8f0 arch/x86/kvm/x86.c:8890
kvm_vcpu_ioctl+0x64f/0xa60 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3163
vfs_ioctl fs/ioctl.c:47 [inline]
ksys_ioctl fs/ioctl.c:771 [inline]
__do_sys_ioctl fs/ioctl.c:780 [inline]
__se_sys_ioctl+0xf9/0x160 fs/ioctl.c:778
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca59
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f24a3aeec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e84e0 RCX: 000000000045ca59
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000003cc R14: 00000000004c6799 R15: 00007f24a3aef6d4
Modules linked in:
CR2: 0000000000000000
---[ end trace cdab85025f649c5c ]---
RIP: 0010:__read_once_size include/linux/compiler.h:252 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x3f/0x60 kernel/kcov.c:202
Code: c2 00 01 ff 00 74 11 f7 c2 00 01 00 00 74 35 83 b9 04 14 00 00 00 74 2c 8b 91 e0 13 00 00 83 fa 02 75 21 48 8b 91 e8 13 00 00 <48> 8b 32 48 8d 7e 01 8b 89 e4 13 00 00 48 39 cf 73 08 48 89 44 f2
RSP: 0018:ffffc90017377758 EFLAGS: 00010246
RAX: ffffffff8119026b RBX: 0000000000000000 RCX: ffff888087f36300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900173778a7 R08: ffffffff811901af R09: ffffc900173778a7
R10: ffffed1013de8882 R11: 0000000000000000 R12: ffff88809f298580
R13: 1ffff92002e6ef13 R14: dffffc0000000000 R15: ffffc90017377898
FS: 00007f24a3aef700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005582a7e62f58 CR3: 0000000092cb6000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[Dmitry Vyukov]

#syz fix: kcov: check kcov_softirq in kcov_remote_stop()

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