linux/arch/x86
Wanpeng Li e2c2206a18 KVM: x86: Fix potential preemption when get the current kvmclock timestamp
BUG: using __this_cpu_read() in preemptible [00000000] code: qemu-system-x86/2809
 caller is __this_cpu_preempt_check+0x13/0x20
 CPU: 2 PID: 2809 Comm: qemu-system-x86 Not tainted 4.11.0+ #13
 Call Trace:
  dump_stack+0x99/0xce
  check_preemption_disabled+0xf5/0x100
  __this_cpu_preempt_check+0x13/0x20
  get_kvmclock_ns+0x6f/0x110 [kvm]
  get_time_ref_counter+0x5d/0x80 [kvm]
  kvm_hv_process_stimers+0x2a1/0x8a0 [kvm]
  ? kvm_hv_process_stimers+0x2a1/0x8a0 [kvm]
  ? kvm_arch_vcpu_ioctl_run+0xac9/0x1ce0 [kvm]
  kvm_arch_vcpu_ioctl_run+0x5bf/0x1ce0 [kvm]
  kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? __fget+0xf3/0x210
  do_vfs_ioctl+0xa4/0x700
  ? __fget+0x114/0x210
  SyS_ioctl+0x79/0x90
  entry_SYSCALL_64_fastpath+0x23/0xc2
 RIP: 0033:0x7f9d164ed357
  ? __this_cpu_preempt_check+0x13/0x20

This can be reproduced by run kvm-unit-tests/hyperv_stimer.flat w/
CONFIG_PREEMPT and CONFIG_DEBUG_PREEMPT enabled.

Safe access to per-CPU data requires a couple of constraints, though: the
thread working with the data cannot be preempted and it cannot be migrated
while it manipulates per-CPU variables. If the thread is preempted, the
thread that replaces it could try to work with the same variables; migration
to another CPU could also cause confusion. However there is no preemption
disable when reads host per-CPU tsc rate to calculate the current kvmclock
timestamp.

This patch fixes it by utilizing get_cpu/put_cpu pair to guarantee both
__this_cpu_read() and rdtsc() are not preempted.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
2017-05-19 19:59:25 +02:00
..
boot x86/mm: Add support for gbpages to kernel_ident_mapping_init() 2017-05-08 08:28:40 +02:00
configs Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-01 20:51:12 -07:00
crypto crypto: glue_helper - remove the le128_gf128mul_x_ble function 2017-04-05 21:58:37 +08:00
entry perf/core improvements and fixes: 2017-05-03 19:28:27 +02:00
events perf/core improvements and fixes: 2017-05-03 19:28:27 +02:00
hyperv char/misc patches for 4.12-rc1 2017-05-04 19:15:35 -07:00
ia32 sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
include KVM: x86: lower default for halt_poll_ns 2017-05-16 21:15:50 +02:00
kernel KVM: x86: Fix load damaged SSEx MXCSR register 2017-05-15 16:08:56 +02:00
kvm KVM: x86: Fix potential preemption when get the current kvmclock timestamp 2017-05-19 19:59:25 +02:00
lguest Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-01 20:51:12 -07:00
lib x86/mm/kaslr: Use the _ASM_MUL macro for multiplication to work around Clang incompatibility 2017-05-05 08:31:05 +02:00
math-emu
mm Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-12 10:11:50 -07:00
net x86: use set_memory.h header 2017-05-08 17:15:13 -07:00
oprofile
pci pci-v4.12-changes 2017-05-08 19:03:25 -07:00
platform x86: use set_memory.h header 2017-05-08 17:15:13 -07:00
power x86/mm: Add support for gbpages to kernel_ident_mapping_init() 2017-05-08 08:28:40 +02:00
purgatory kasan: do not sanitize kexec purgatory 2017-03-31 17:13:30 -07:00
ras RAS: Add a Corrected Errors Collector 2017-03-28 08:54:48 +02:00
realmode x86: use set_memory.h header 2017-05-08 17:15:13 -07:00
tools
um Merge branch 'for-linus-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml 2017-05-13 10:20:02 -07:00
video
xen xen: adjust early dom0 p2m handling to xen hypervisor behavior 2017-05-11 15:55:20 +02:00
.gitignore
Kbuild Drivers: hv vmbus: Move Hypercall page setup out of common code 2017-01-19 11:42:07 +01:00
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching 2017-05-02 18:24:16 -07:00
Kconfig.cpu
Kconfig.debug usb/early: Add driver for xhci debug capability 2017-03-21 12:30:05 +01:00
Makefile x86/build: Don't add -maccumulate-outgoing-args w/o compiler support 2017-05-09 08:16:45 +02:00
Makefile_32.cpu x86/build: Mostly disable '-maccumulate-outgoing-args' 2017-03-30 11:53:04 +02:00
Makefile.um