[syzbot] WARNING in emulate_vsyscall

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    0f4498ce Merge tag 'for-5.12/dm-fixes-2' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1658754ed00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=daeff30c2474a60f
dashboard link: https://syzkaller.appspot.com/bug?extid=2698183e871d8a137f9d
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122aab01d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11004d06d00000

The issue was bisected to:

commit 5042d40a264c8a508d58ed71e4c07b05175b3635
Author: Andy Lutomirski <luto@xxxxxxxxxx>
Date:   Wed Feb 10 02:33:42 2021 +0000

    x86/fault: Bypass no_context() for implicit kernel faults from usermode

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1004e126d00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1204e126d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=1404e126d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2698183e871d8a137f9d@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")

syz-executor412[8390] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7ffe5492ae00 ax:ffffffffffffffda si:600000001 di:aa060
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8390 at arch/x86/entry/vsyscall/vsyscall_64.c:276 emulate_vsyscall+0x317/0xbf0 arch/x86/entry/vsyscall/vsyscall_64.c:276
Modules linked in:
CPU: 1 PID: 8390 Comm: syz-executor412 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:emulate_vsyscall+0x317/0xbf0 arch/x86/entry/vsyscall/vsyscall_64.c:276
Code: 80 01 00 00 e8 0a 88 73 00 48 c1 eb 0a 31 ff 41 bc 01 00 00 00 f7 d3 83 e3 01 89 de e8 a2 8f 73 00 85 db 74 0f e8 e9 87 73 00 <0f> 0b e9 44 01 00 00 45 31 e4 e8 da 87 73 00 44 89 e0 48 83 c4 38
RSP: 0000:ffffc9000151fe48 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff888017243880 RSI: ffffffff81006987 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8100697e R11: 0000000000000000 R12: 0000000000000001
R13: ffffc9000151ffd8 R14: ffffc9000151fff0 R15: 0000000000000000
FS:  00000000006c63c0(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fae07369000 CR3: 0000000018320000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 do_user_addr_fault+0x9a5/0x1210 arch/x86/mm/fault.c:1314
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x9e/0x180 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577
RIP: 0033:_end+0x6f3da000/0x0
Code: Unable to access opcode bytes at RIP 0xffffffffff5fffd6.
RSP: 002b:00007ffe5492ae00 EFLAGS: 00010246
RAX: ffffffffffffffda RBX: 0000000000001000 RCX: 00000000000266c5
RDX: 0000000000001000 RSI: 0000000600000001 RDI: 00000000000aa060
RBP: 00000000000812c1 R08: 0000000000483000 R09: 0000000000483000
R10: 0000000000083000 R11: 0000000400000001 R12: 00000000000812c1
R13: 0000000000401000 R14: 0000000000401000 R15: 0000000000001000


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