Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") applied a patch from upstream, but it appears that it wasn't backported correctly to 4.14. The extra out_fpu label and kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling kvm_put_guest_fpu() twice in a row, corrupting guest state.
Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") Signed-off-by: Daniel Verkamp dverkamp@chromium.org ---
I'm unsure if this is the right way to send this fix - there is no corresponding mainline commit to reference, since the code there is already correct, and the problem was introduced in the cherry-picked stable backport. Please let me know if there's a different process for fixes to stable-only issues.
arch/x86/kvm/x86.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 130be2efafbe..3e767430d3b2 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7430,7 +7430,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) vcpu->arch.complete_userspace_io = NULL; r = cui(vcpu); if (r <= 0) - goto out_fpu; + goto out; } else WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
@@ -7439,8 +7439,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) else r = vcpu_run(vcpu);
-out_fpu: - kvm_put_guest_fpu(vcpu); out: kvm_put_guest_fpu(vcpu); post_kvm_run_save(vcpu);
Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") applied a patch from upstream, but it appears that it wasn't backported correctly to 4.14. The extra out_fpu label and kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling kvm_put_guest_fpu() twice in a row, corrupting guest state. Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of the function.
Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") Signed-off-by: Daniel Verkamp dverkamp@chromium.org ---
v2: removed additional redundant kvm_load_guest_fpu()
I'm unsure if this is the right way to send this fix - there is no corresponding mainline commit to reference, since the code there is already correct, and the problem was introduced in the cherry-picked stable backport. Please let me know if there's a different process for fixes to stable-only issues.
---
arch/x86/kvm/x86.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 130be2efafbe..af7ab2c71786 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7423,14 +7423,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) } }
- kvm_load_guest_fpu(vcpu); - if (unlikely(vcpu->arch.complete_userspace_io)) { int (*cui)(struct kvm_vcpu *) = vcpu->arch.complete_userspace_io; vcpu->arch.complete_userspace_io = NULL; r = cui(vcpu); if (r <= 0) - goto out_fpu; + goto out; } else WARN_ON(vcpu->arch.pio.count || vcpu->mmio_needed);
@@ -7439,8 +7437,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) else r = vcpu_run(vcpu);
-out_fpu: - kvm_put_guest_fpu(vcpu); out: kvm_put_guest_fpu(vcpu); post_kvm_run_save(vcpu);
On Wed, Jan 30, 2019 at 2:29 PM Daniel Verkamp dverkamp@chromium.org wrote:
Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") applied a patch from upstream, but it appears that it wasn't backported correctly to 4.14. The extra out_fpu label and kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling kvm_put_guest_fpu() twice in a row, corrupting guest state. Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of the function.
Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") Signed-off-by: Daniel Verkamp dverkamp@chromium.org
v2: removed additional redundant kvm_load_guest_fpu()
I'm unsure if this is the right way to send this fix - there is no corresponding mainline commit to reference, since the code there is already correct, and the problem was introduced in the cherry-picked stable backport. Please let me know if there's a different process for fixes to stable-only issues.
Please ignore this - I had checked last week and it seemed no-one had reported this, but now it looks like an identical fix was already posted: https://www.spinics.net/lists/stable/msg282163.html
Sorry for the noise!
Thanks, -- Daniel
On Wed, Jan 30, 2019 at 02:29:26PM -0800, Daniel Verkamp wrote:
Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") applied a patch from upstream, but it appears that it wasn't backported correctly to 4.14. The extra out_fpu label and kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling kvm_put_guest_fpu() twice in a row, corrupting guest state. Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of the function.
Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") Signed-off-by: Daniel Verkamp dverkamp@chromium.org
v2: removed additional redundant kvm_load_guest_fpu()
I'm unsure if this is the right way to send this fix - there is no corresponding mainline commit to reference, since the code there is already correct, and the problem was introduced in the cherry-picked stable backport. Please let me know if there's a different process for fixes to stable-only issues.
This should now be fixed with 9485d5d2318b ("KVM: x86: Fix a 4.14 backport regression related to userspace/guest FPU") in the 4.14.97 release that just happened, right?
thanks,
greg k-h
Yes, please disregard this patch - I had this on my to-do list to investigate and missed the stable update that fixed it already.
Thanks, -- Daniel
On Wed, Jan 30, 2019 at 11:18 PM Greg KH gregkh@linuxfoundation.org wrote:
On Wed, Jan 30, 2019 at 02:29:26PM -0800, Daniel Verkamp wrote:
Commit 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") applied a patch from upstream, but it appears that it wasn't backported correctly to 4.14. The extra out_fpu label and kvm_put_guest_fpu() added in kvm_arch_vcpu_ioctl_run() result in calling kvm_put_guest_fpu() twice in a row, corrupting guest state. Additionally, a duplicate kvm_load_guest_fpu() is added in the middle of the function.
Fixes: 4124a4cff344 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run") Signed-off-by: Daniel Verkamp dverkamp@chromium.org
v2: removed additional redundant kvm_load_guest_fpu()
I'm unsure if this is the right way to send this fix - there is no corresponding mainline commit to reference, since the code there is already correct, and the problem was introduced in the cherry-picked stable backport. Please let me know if there's a different process for fixes to stable-only issues.
This should now be fixed with 9485d5d2318b ("KVM: x86: Fix a 4.14 backport regression related to userspace/guest FPU") in the 4.14.97 release that just happened, right?
thanks,
greg k-h
linux-stable-mirror@lists.linaro.org
-
Daniel Verkamp -
Greg KH