* [PATCH] KVM: SVM: Initialize prev_ga_tag before use
@ 2020-10-03 23:27 Suravee Suthikulpanit
2020-10-09 11:06 ` Suravee Suthikulpanit
2020-10-19 15:54 ` Paolo Bonzini
0 siblings, 2 replies; 3+ messages in thread
From: Suravee Suthikulpanit @ 2020-10-03 23:27 UTC (permalink / raw)
To: linux-kernel, kvm; +Cc: pbonzini, joro, Suravee Suthikulpanit
The function amd_ir_set_vcpu_affinity makes use of the parameter struct
amd_iommu_pi_data.prev_ga_tag to determine if it should delete struct
amd_iommu_pi_data from a list when not running in AVIC mode.
However, prev_ga_tag is initialized only when AVIC is enabled. The non-zero
uninitialized value can cause unintended code path, which ends up making
use of the struct vcpu_svm.ir_list and ir_list_lock without being
initialized (since they are intended only for the AVIC case).
This triggers NULL pointer dereference bug in the function vm_ir_list_del
with the following call trace:
svm_update_pi_irte+0x3c2/0x550 [kvm_amd]
? proc_create_single_data+0x41/0x50
kvm_arch_irq_bypass_add_producer+0x40/0x60 [kvm]
__connect+0x5f/0xb0 [irqbypass]
irq_bypass_register_producer+0xf8/0x120 [irqbypass]
vfio_msi_set_vector_signal+0x1de/0x2d0 [vfio_pci]
vfio_msi_set_block+0x77/0xe0 [vfio_pci]
vfio_pci_set_msi_trigger+0x25c/0x2f0 [vfio_pci]
vfio_pci_set_irqs_ioctl+0x88/0xb0 [vfio_pci]
vfio_pci_ioctl+0x2ea/0xed0 [vfio_pci]
? alloc_file_pseudo+0xa5/0x100
vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
? vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
__x64_sys_ioctl+0x96/0xd0
do_syscall_64+0x37/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Therefore, initialize prev_ga_tag to zero before use. This should be safe
because ga_tag value 0 is invalid (see function avic_vm_init).
Fixes: dfa20099e26e ("KVM: SVM: Refactor AVIC vcpu initialization into avic_init_vcpu()")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
arch/x86/kvm/svm/avic.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index ac830cd50830..381d22daa4ac 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -868,6 +868,7 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
* - Tell IOMMU to use legacy mode for this interrupt.
* - Retrieve ga_tag of prior interrupt remapping data.
*/
+ pi.prev_ga_tag = 0;
pi.is_guest_mode = false;
ret = irq_set_vcpu_affinity(host_irq, &pi);
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: SVM: Initialize prev_ga_tag before use
2020-10-03 23:27 [PATCH] KVM: SVM: Initialize prev_ga_tag before use Suravee Suthikulpanit
@ 2020-10-09 11:06 ` Suravee Suthikulpanit
2020-10-19 15:54 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Suravee Suthikulpanit @ 2020-10-09 11:06 UTC (permalink / raw)
To: linux-kernel, kvm; +Cc: pbonzini, joro
Paolo,
Are there any issues or concerns about this patch?
Thank you,
Suravee
On 10/4/20 6:27 AM, Suravee Suthikulpanit wrote:
> The function amd_ir_set_vcpu_affinity makes use of the parameter struct
> amd_iommu_pi_data.prev_ga_tag to determine if it should delete struct
> amd_iommu_pi_data from a list when not running in AVIC mode.
>
> However, prev_ga_tag is initialized only when AVIC is enabled. The non-zero
> uninitialized value can cause unintended code path, which ends up making
> use of the struct vcpu_svm.ir_list and ir_list_lock without being
> initialized (since they are intended only for the AVIC case).
>
> This triggers NULL pointer dereference bug in the function vm_ir_list_del
> with the following call trace:
>
> svm_update_pi_irte+0x3c2/0x550 [kvm_amd]
> ? proc_create_single_data+0x41/0x50
> kvm_arch_irq_bypass_add_producer+0x40/0x60 [kvm]
> __connect+0x5f/0xb0 [irqbypass]
> irq_bypass_register_producer+0xf8/0x120 [irqbypass]
> vfio_msi_set_vector_signal+0x1de/0x2d0 [vfio_pci]
> vfio_msi_set_block+0x77/0xe0 [vfio_pci]
> vfio_pci_set_msi_trigger+0x25c/0x2f0 [vfio_pci]
> vfio_pci_set_irqs_ioctl+0x88/0xb0 [vfio_pci]
> vfio_pci_ioctl+0x2ea/0xed0 [vfio_pci]
> ? alloc_file_pseudo+0xa5/0x100
> vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
> ? vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
> __x64_sys_ioctl+0x96/0xd0
> do_syscall_64+0x37/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Therefore, initialize prev_ga_tag to zero before use. This should be safe
> because ga_tag value 0 is invalid (see function avic_vm_init).
>
> Fixes: dfa20099e26e ("KVM: SVM: Refactor AVIC vcpu initialization into avic_init_vcpu()")
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
> arch/x86/kvm/svm/avic.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index ac830cd50830..381d22daa4ac 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -868,6 +868,7 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
> * - Tell IOMMU to use legacy mode for this interrupt.
> * - Retrieve ga_tag of prior interrupt remapping data.
> */
> + pi.prev_ga_tag = 0;
> pi.is_guest_mode = false;
> ret = irq_set_vcpu_affinity(host_irq, &pi);
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] KVM: SVM: Initialize prev_ga_tag before use
2020-10-03 23:27 [PATCH] KVM: SVM: Initialize prev_ga_tag before use Suravee Suthikulpanit
2020-10-09 11:06 ` Suravee Suthikulpanit
@ 2020-10-19 15:54 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2020-10-19 15:54 UTC (permalink / raw)
To: Suravee Suthikulpanit, linux-kernel, kvm; +Cc: joro
On 04/10/20 01:27, Suravee Suthikulpanit wrote:
> The function amd_ir_set_vcpu_affinity makes use of the parameter struct
> amd_iommu_pi_data.prev_ga_tag to determine if it should delete struct
> amd_iommu_pi_data from a list when not running in AVIC mode.
>
> However, prev_ga_tag is initialized only when AVIC is enabled. The non-zero
> uninitialized value can cause unintended code path, which ends up making
> use of the struct vcpu_svm.ir_list and ir_list_lock without being
> initialized (since they are intended only for the AVIC case).
>
> This triggers NULL pointer dereference bug in the function vm_ir_list_del
> with the following call trace:
>
> svm_update_pi_irte+0x3c2/0x550 [kvm_amd]
> ? proc_create_single_data+0x41/0x50
> kvm_arch_irq_bypass_add_producer+0x40/0x60 [kvm]
> __connect+0x5f/0xb0 [irqbypass]
> irq_bypass_register_producer+0xf8/0x120 [irqbypass]
> vfio_msi_set_vector_signal+0x1de/0x2d0 [vfio_pci]
> vfio_msi_set_block+0x77/0xe0 [vfio_pci]
> vfio_pci_set_msi_trigger+0x25c/0x2f0 [vfio_pci]
> vfio_pci_set_irqs_ioctl+0x88/0xb0 [vfio_pci]
> vfio_pci_ioctl+0x2ea/0xed0 [vfio_pci]
> ? alloc_file_pseudo+0xa5/0x100
> vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
> ? vfio_device_fops_unl_ioctl+0x26/0x30 [vfio]
> __x64_sys_ioctl+0x96/0xd0
> do_syscall_64+0x37/0x80
> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Therefore, initialize prev_ga_tag to zero before use. This should be safe
> because ga_tag value 0 is invalid (see function avic_vm_init).
>
> Fixes: dfa20099e26e ("KVM: SVM: Refactor AVIC vcpu initialization into avic_init_vcpu()")
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> ---
> arch/x86/kvm/svm/avic.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index ac830cd50830..381d22daa4ac 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -868,6 +868,7 @@ int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
> * - Tell IOMMU to use legacy mode for this interrupt.
> * - Retrieve ga_tag of prior interrupt remapping data.
> */
> + pi.prev_ga_tag = 0;
> pi.is_guest_mode = false;
> ret = irq_set_vcpu_affinity(host_irq, &pi);
>
>
Queued (with Cc: stable), thanks.
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-10-19 15:54 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-03 23:27 [PATCH] KVM: SVM: Initialize prev_ga_tag before use Suravee Suthikulpanit
2020-10-09 11:06 ` Suravee Suthikulpanit
2020-10-19 15:54 ` Paolo Bonzini
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).