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Subject[syzbot] WARNING in fixup_exception
From
Hello,

syzbot found the following issue on:

HEAD commit: 800829388818 mm: vmscan: reduce throttling due to a failur..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=100bafc3b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=1a86c22260afac2f
dashboard link: https://syzkaller.appspot.com/bug?extid=d9a0f6db5058ce56e260
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=154be92bb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=112fd30bb00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d9a0f6db5058ce56e260@syzkaller.appspotmail.com

------------[ cut here ]------------
General protection fault in user access. Non-canonical address?
WARNING: CPU: 0 PID: 2529 at arch/x86/mm/extable.c:57 ex_handler_uaccess arch/x86/mm/extable.c:57 [inline]
WARNING: CPU: 0 PID: 2529 at arch/x86/mm/extable.c:57 fixup_exception+0x5da/0x690 arch/x86/mm/extable.c:140
Modules linked in:
CPU: 0 PID: 2529 Comm: syz-executor223 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ex_handler_uaccess arch/x86/mm/extable.c:57 [inline]
RIP: 0010:fixup_exception+0x5da/0x690 arch/x86/mm/extable.c:140
Code: 0c 31 ff 89 de e8 06 f5 42 00 84 db 0f 85 9b fc ff ff e8 19 f1 42 00 48 c7 c7 20 59 a9 89 c6 05 49 33 48 0c 01 e8 52 cf cb 07 <0f> 0b e9 7c fc ff ff e8 fa f0 42 00 48 89 de 48 c7 c7 c0 59 a9 89
RSP: 0018:ffffc90003bf7bf0 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801dbd0000 RSI: ffffffff815f0948 RDI: fffff5200077ef70
RBP: ffffffff8b6d0044 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815ea6ee R11: 0000000000000000 R12: ffffc90003bf7cc8
R13: 000000000000000d R14: ffffc90003bf7d48 R15: 0000000000000000
FS: 00007f46f7487700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f46f7d44190 CR3: 0000000022544000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__exc_general_protection arch/x86/kernel/traps.c:601 [inline]
exc_general_protection+0xed/0x300 arch/x86/kernel/traps.c:562
asm_exc_general_protection+0x1e/0x30 arch/x86/include/asm/idtentry.h:562
RIP: 0010:__put_user_nocheck_2+0x3/0x11
Code: 00 00 48 39 d9 73 74 0f 01 cb 88 01 31 c9 0f 01 ca c3 66 0f 1f 44 00 00 48 bb ff ef ff ff ff 7f 00 00 48 39 d9 73 54 0f 01 cb <66> 89 01 31 c9 0f 01 ca c3 0f 1f 44 00 00 48 bb fd ef ff ff ff 7f
RSP: 0018:ffffc90003bf7d78 EFLAGS: 00050293
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0006020200000004
RDX: ffff88801dbd0000 RSI: ffffffff86d1fba8 RDI: 0000000000000003
RBP: ffff888077ff01a8 R08: 0000000000000002 R09: 0000000000000001
R10: ffffffff86d1fb95 R11: 0000000000000000 R12: 0006020200000004
R13: ffff888077ff0258 R14: 0000000000000000 R15: 0000000000000000
vhost_put_used_flags drivers/vhost/vhost.c:969 [inline]
vhost_update_used_flags+0x1a3/0x3d0 drivers/vhost/vhost.c:1969
vhost_vq_init_access+0x114/0x5c0 drivers/vhost/vhost.c:2013
vhost_net_set_backend drivers/vhost/net.c:1548 [inline]
vhost_net_ioctl+0xbad/0x1740 drivers/vhost/net.c:1705
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f46f7d02839
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 31 19 00 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f46f7487208 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f46f7d8a278 RCX: 00007f46f7d02839
RDX: 0000000020000000 RSI: 000000004008af30 RDI: 0000000000000003
RBP: 00007f46f7d8a270 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f46f7d8a27c
R13: 00007ffc8471e10f R14: 00007f46f7487300 R15: 0000000000022000
</TASK>
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 48 39 d9 cmp %rbx,%rcx
5: 73 74 jae 0x7b
7: 0f 01 cb stac
a: 88 01 mov %al,(%rcx)
c: 31 c9 xor %ecx,%ecx
e: 0f 01 ca clac
11: c3 retq
12: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
18: 48 bb ff ef ff ff ff movabs $0x7fffffffefff,%rbx
1f: 7f 00 00
22: 48 39 d9 cmp %rbx,%rcx
25: 73 54 jae 0x7b
27: 0f 01 cb stac
* 2a: 66 89 01 mov %ax,(%rcx) <-- trapping instruction
2d: 31 c9 xor %ecx,%ecx
2f: 0f 01 ca clac
32: c3 retq
33: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
38: 48 rex.W
39: bb fd ef ff ff mov $0xffffeffd,%ebx
3e: ff (bad)
3f: 7f .byte 0x7f


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

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