Hi Al,

We noticed the below oops since commit 68a25f08c9bec07ad95e55a01b127168e43aed84
("process_vm_access: take get_user_pages/put_pages one level up")
while running ltp tests inside kvm.

[  466.193846] BUG: unable to handle kernel paging request at fffffff27b92dd20
[  466.195225] IP: [<ffffffff81190d7f>] put_page+0x5/0x28
[  466.196263] PGD 220d067 PUD 0
[  466.197137] Oops: 0000 [#1] SMP
[  466.197261] Modules linked in: msr microcode processor
[  466.197261] CPU: 2 PID: 30338 Comm: process_vm01 Not tainted 3.14.0-rc1-00027-g68a25f0 #1
[  466.197261] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  466.197261] task: ffff88007c11ecc0 ti: ffff88007b92c000 task.ti: ffff88007b92c000
[  466.197261] RIP: 0010:[<ffffffff81190d7f>]  [<ffffffff81190d7f>] put_page+0x5/0x28
[  466.197261] RSP: 0018:ffff88007b92dc98  EFLAGS: 00010286
[  466.197261] RAX: fffffffffffffff0 RBX: 0000000000000000 RCX: 0000000000001000
[  466.197261] RDX: 0000000000000000 RSI: 0000000097230000 RDI: fffffff27b92dd20
[  466.197261] RBP: ffff88007b92dde8 R08: 0000000000000000 R09: 00007fe39722f001
[  466.197261] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88007c11ecc0
[  466.197261] R13: ffff88007b92dd40 R14: fffffffffffffff2 R15: ffff88007b92de10
[  466.197261] FS:  00007fe397228700(0000) GS:ffff88011fd00000(0000) knlGS:0000000000000000
[  466.197261] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  466.197261] CR2: fffffff27b92dd20 CR3: 000000007f537000 CR4: 00000000000006e0
[  466.197261] Stack:
[  466.197261]  ffffffff811b7ea1 ffff88007b92dd40 0000000000000000 000000000000000d
[  466.197261]  ffffffff81f7ad76 fffffff27b92dd20 ffff88007baa4420 0000000000000001
[  466.197261]  0000000000000000 ffff88007b92deb0 0000000000001000 0000000000000001
[  466.197261] Call Trace:
[  466.197261]  [<ffffffff811b7ea1>] ? process_vm_rw_core.isra.1+0x39f/0x444
[  466.197261]  [<ffffffff811aadbb>] ? handle_mm_fault+0x9e9/0xc9c
[  466.197261]  [<ffffffff811a65f0>] ? might_fault+0x3e/0x40
[  466.197261]  [<ffffffff811e2264>] ? rw_copy_check_uvector+0x6f/0xfd
[  466.197261]  [<ffffffff811b8017>] process_vm_rw+0xd1/0x117
[  466.197261]  [<ffffffff811b05ae>] ? do_mmap_pgoff+0x2e1/0x34c
[  466.197261]  [<ffffffff8119d9fe>] ? vm_mmap_pgoff+0x72/0x94
[  466.197261]  [<ffffffff81a2eb5e>] ? do_page_fault+0xe/0x10
[  466.197261]  [<ffffffff8151472b>] ? trace_hardirqs_on_thunk+0x3a/0x3c
[  466.197261]  [<ffffffff811b8073>] SyS_process_vm_readv+0x16/0x18
[  466.197261]  [<ffffffff81a32b29>] system_call_fastpath+0x16/0x1b

Attached is the full dmesg.

Thanks,
Fengguang