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Zhuang Yanying a13d21ed85 KVM: fix overflow of zero page refcount with ksm running 
[ Upstream commit 7df003c85218b5f5b10a7f6418208f31e813f38f ]

We are testing Virtual Machine with KSM on v5.4-rc2 kernel,
and found the zero_page refcount overflow.
The cause of refcount overflow is increased in try_async_pf
(get_user_page) without being decreased in mmu_set_spte()
while handling ept violation.
In kvm_release_pfn_clean(), only unreserved page will call
put_page. However, zero page is reserved.
So, as well as creating and destroy vm, the refcount of
zero page will continue to increase until it overflows.

step1:
echo 10000 > /sys/kernel/pages_to_scan/pages_to_scan
echo 1 > /sys/kernel/pages_to_scan/run
echo 1 > /sys/kernel/pages_to_scan/use_zero_pages

step2:
just create several normal qemu kvm vms.
And destroy it after 10s.
Repeat this action all the time.

After a long period of time, all domains hang because
of the refcount of zero page overflow.

Qemu print error log as follow:
 …
 error: kvm run failed Bad address
 EAX=00006cdc EBX=00000008 ECX=80202001 EDX=078bfbfd
 ESI=ffffffff EDI=00000000 EBP=00000008 ESP=00006cc4
 EIP=000efd75 EFL=00010002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
 ES =0010 00000000 ffffffff 00c09300 DPL=0 DS   [-WA]
 CS =0008 00000000 ffffffff 00c09b00 DPL=0 CS32 [-RA]
 SS =0010 00000000 ffffffff 00c09300 DPL=0 DS   [-WA]
 DS =0010 00000000 ffffffff 00c09300 DPL=0 DS   [-WA]
 FS =0010 00000000 ffffffff 00c09300 DPL=0 DS   [-WA]
 GS =0010 00000000 ffffffff 00c09300 DPL=0 DS   [-WA]
 LDT=0000 00000000 0000ffff 00008200 DPL=0 LDT
 TR =0000 00000000 0000ffff 00008b00 DPL=0 TSS32-busy
 GDT=     000f7070 00000037
 IDT=     000f70ae 00000000
 CR0=00000011 CR2=00000000 CR3=00000000 CR4=00000000
 DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
 DR6=00000000ffff0ff0 DR7=0000000000000400
 EFER=0000000000000000
 Code=00 01 00 00 00 e9 e8 00 00 00 c7 05 4c 55 0f 00 01 00 00 00 <8b> 35 00 00 01 00 8b 3d 04 00 01 00 b8 d8 d3 00 00 c1 e0 08 0c ea a3 00 00 01 00 c7 05 04
 …

Meanwhile, a kernel warning is departed.

 [40914.836375] WARNING: CPU: 3 PID: 82067 at ./include/linux/mm.h:987 try_get_page+0x1f/0x30
 [40914.836412] CPU: 3 PID: 82067 Comm: CPU 0/KVM Kdump: loaded Tainted: G           OE     5.2.0-rc2 #5
 [40914.836415] RIP: 0010:try_get_page+0x1f/0x30
 [40914.836417] Code: 40 00 c3 0f 1f 84 00 00 00 00 00 48 8b 47 08 a8 01 75 11 8b 47 34 85 c0 7e 10 f0 ff 47 34 b8 01 00 00 00 c3 48 8d 78 ff eb e9 <0f> 0b 31 c0 c3 66 90 66 2e 0f 1f 84 00 0
 0 00 00 00 48 8b 47 08 a8
 [40914.836418] RSP: 0018:ffffb4144e523988 EFLAGS: 00010286
 [40914.836419] RAX: 0000000080000000 RBX: 0000000000000326 RCX: 0000000000000000
 [40914.836420] RDX: 0000000000000000 RSI: 00004ffdeba10000 RDI: ffffdf07093f6440
 [40914.836421] RBP: ffffdf07093f6440 R08: 800000424fd91225 R09: 0000000000000000
 [40914.836421] R10: ffff9eb41bfeebb8 R11: 0000000000000000 R12: ffffdf06bbd1e8a8
 [40914.836422] R13: 0000000000000080 R14: 800000424fd91225 R15: ffffdf07093f6440
 [40914.836423] FS:  00007fb60ffff700(0000) GS:ffff9eb4802c0000(0000) knlGS:0000000000000000
 [40914.836425] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [40914.836426] CR2: 0000000000000000 CR3: 0000002f220e6002 CR4: 00000000003626e0
 [40914.836427] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 [40914.836427] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 [40914.836428] Call Trace:
 [40914.836433]  follow_page_pte+0x302/0x47b
 [40914.836437]  __get_user_pages+0xf1/0x7d0
 [40914.836441]  ? irq_work_queue+0x9/0x70
 [40914.836443]  get_user_pages_unlocked+0x13f/0x1e0
 [40914.836469]  __gfn_to_pfn_memslot+0x10e/0x400 [kvm]
 [40914.836486]  try_async_pf+0x87/0x240 [kvm]
 [40914.836503]  tdp_page_fault+0x139/0x270 [kvm]
 [40914.836523]  kvm_mmu_page_fault+0x76/0x5e0 [kvm]
 [40914.836588]  vcpu_enter_guest+0xb45/0x1570 [kvm]
 [40914.836632]  kvm_arch_vcpu_ioctl_run+0x35d/0x580 [kvm]
 [40914.836645]  kvm_vcpu_ioctl+0x26e/0x5d0 [kvm]
 [40914.836650]  do_vfs_ioctl+0xa9/0x620
 [40914.836653]  ksys_ioctl+0x60/0x90
 [40914.836654]  __x64_sys_ioctl+0x16/0x20
 [40914.836658]  do_syscall_64+0x5b/0x180
 [40914.836664]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 [40914.836666] RIP: 0033:0x7fb61cb6bfc7

Signed-off-by: LinFeng <linfeng23@huawei.com>
Signed-off-by: Zhuang Yanying <ann.zhuangyanying@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
 		2020-10-01 13:17:31 +02:00
Documentation affs: fix basic permission bits to actually work 2020-09-09 19:12:34 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch ARM: 8948/1: Prevent OOB access in stacktrace 2020-10-01 13:17:29 +02:00
block block: only call sched requeue_request() for scheduled requests 2020-09-23 12:40:37 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: af_alg - Work around empty control messages without MSG_MORE 2020-09-03 11:27:05 +02:00
drivers ar5523: Add USB ID of SMCWUSBT-G2 wireless adapter 2020-10-01 13:17:29 +02:00
fs ceph: ensure we have a new cap before continuing in fill_inode 2020-10-01 13:17:29 +02:00
include sctp: move trace_sctp_probe_path into sctp_outq_sack 2020-10-01 13:17:27 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel tracing: Set kernel_stack's caller size properly 2020-10-01 13:17:29 +02:00
lib kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec() 2020-10-01 13:17:10 +02:00
mm mm: pagewalk: fix termination condition in walk_pte_range() 2020-10-01 13:17:30 +02:00
net Bluetooth: prefetch channel before killing sock 2020-10-01 13:17:31 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts checkpatch: fix the usage of capture group ( ... ) 2020-09-09 19:12:37 +02:00
security selinux: allow labeling before policy is loaded 2020-10-01 13:17:10 +02:00
sound ALSA: hda: enable regmap internal locking 2020-10-01 13:17:24 +02:00
tools tools/power/x86/intel_pstate_tracer: changes for python 3 compatibility 2020-10-01 13:17:30 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: fix overflow of zero page refcount with ksm running 2020-10-01 13:17:31 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.68 2020-09-26 18:03:16 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.