[syzbot] general protection fault in unlink_anon_vmas (2)

[syzbot <syzbot+83dc7d9efc6d710e264d@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    fa54d366a6e4 Merge tag 'acpi-5.14-rc7' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=179ed189300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f61012d0b1cd846f
dashboard link: https://syzkaller.appspot.com/bug?extid=83dc7d9efc6d710e264d
compiler:       Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

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+83dc7d9efc6d710e264d@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000014: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000a0-0x00000000000000a7]
CPU: 1 PID: 11237 Comm: systemd-udevd Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:unlink_anon_vmas+0x21f/0x600 mm/rmap.c:409
Code: 00 00 00 00 00 fc ff df 42 80 3c 28 00 74 08 48 89 ef e8 d4 51 0d 00 48 8b 5d 00 b8 a4 00 00 00 48 01 c3 48 89 d8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 4c 8b 7c 24 10 0f 85 cc 00 00 00 ff 0b 48 8b
RSP: 0018:ffffc900023ff9e8 EFLAGS: 00010207
RAX: 0000000000000014 RBX: 00000000000000a4 RCX: ffff888071edb880
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffff88800010f1a8 R08: ffffffff81b54680 R09: ffffed100257e5e3
R10: ffffed100257e5e3 R11: 0000000000000000 R12: ffff88807b5e6078
R13: dffffc0000000000 R14: 1ffff1100dd0c1ec R15: ffff88806e860f60
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055bb059c2928 CR3: 0000000078608000 CR4: 00000000001526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 free_pgtables+0x190/0x2d0 mm/memory.c:426
 exit_mmap+0x3fc/0x7a0 mm/mmap.c:3202
 __mmput+0x111/0x370 kernel/fork.c:1101
 exit_mm+0x60a/0x770 kernel/exit.c:501
 do_exit+0x6ae/0x2510 kernel/exit.c:812
 do_group_exit+0x168/0x2d0 kernel/exit.c:922
 __do_sys_exit_group+0x13/0x20 kernel/exit.c:933
 __se_sys_exit_group+0x10/0x10 kernel/exit.c:931
 __x64_sys_exit_group+0x37/0x40 kernel/exit.c:931
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f32b0229618
Code: Unable to access opcode bytes at RIP 0x7f32b02295ee.
RSP: 002b:00007fff87af41c8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fff87af4290 RCX: 00007f32b0229618
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00007fff87af4340 R08: 00000000000000e7 R09: fffffffffffffe50
R10: 00000000ffffffff R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000003 R15: 000000000000000e
Modules linked in:
---[ end trace b77ca344fbcca8ec ]---
RIP: 0010:unlink_anon_vmas+0x21f/0x600 mm/rmap.c:409
Code: 00 00 00 00 00 fc ff df 42 80 3c 28 00 74 08 48 89 ef e8 d4 51 0d 00 48 8b 5d 00 b8 a4 00 00 00 48 01 c3 48 89 d8 48 c1 e8 03 <42> 0f b6 04 28 84 c0 4c 8b 7c 24 10 0f 85 cc 00 00 00 ff 0b 48 8b
RSP: 0018:ffffc900023ff9e8 EFLAGS: 00010207
RAX: 0000000000000014 RBX: 00000000000000a4 RCX: ffff888071edb880
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffff88800010f1a8 R08: ffffffff81b54680 R09: ffffed100257e5e3
R10: ffffed100257e5e3 R11: 0000000000000000 R12: ffff88807b5e6078
R13: dffffc0000000000 R14: 1ffff1100dd0c1ec R15: ffff88806e860f60
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd068008020 CR3: 0000000023261000 CR4: 00000000001526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 7 bytes skipped:
   0:	df 42 80             	filds  -0x80(%rdx)
   3:	3c 28                	cmp    $0x28,%al
   5:	00 74 08 48          	add    %dh,0x48(%rax,%rcx,1)
   9:	89 ef                	mov    %ebp,%edi
   b:	e8 d4 51 0d 00       	callq  0xd51e4
  10:	48 8b 5d 00          	mov    0x0(%rbp),%rbx
  14:	b8 a4 00 00 00       	mov    $0xa4,%eax
  19:	48 01 c3             	add    %rax,%rbx
  1c:	48 89 d8             	mov    %rbx,%rax
  1f:	48 c1 e8 03          	shr    $0x3,%rax
* 23:	42 0f b6 04 28       	movzbl (%rax,%r13,1),%eax <-- trapping instruction
  28:	84 c0                	test   %al,%al
  2a:	4c 8b 7c 24 10       	mov    0x10(%rsp),%r15
  2f:	0f 85 cc 00 00 00    	jne    0x101
  35:	ff 0b                	decl   (%rbx)
  37:	48                   	rex.W
  38:	8b                   	.byte 0x8b


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