From 16cbec24897624051b324aa3a85859c38ca65fde Mon Sep 17 00:00:00 2001 From: Stanislav Kinsburskii Date: Tue, 24 Mar 2026 23:57:40 +0000 Subject: mshv: Fix infinite fault loop on permission-denied GPA intercepts Prevent infinite fault loops when guests access memory regions without proper permissions. Currently, mshv_handle_gpa_intercept() attempts to remap pages for all faults on movable memory regions, regardless of whether the access type is permitted. When a guest writes to a read-only region, the remap succeeds but the region remains read-only, causing immediate re-fault and spinning the vCPU indefinitely. Validate intercept access type against region permissions before attempting remaps. Reject writes to non-writable regions and executes to non-executable regions early, returning false to let the VMM handle the intercept appropriately. This also closes a potential DoS vector where malicious guests could intentionally trigger these fault loops to consume host resources. Fixes: b9a66cd5ccbb ("mshv: Add support for movable memory regions") Signed-off-by: Stanislav Kinsburskii Reviewed-by: Anirudh Rayabharam (Microsoft) Signed-off-by: Wei Liu --- include/hyperv/hvgdk_mini.h | 6 ++++++ include/hyperv/hvhdk.h | 4 ++-- 2 files changed, 8 insertions(+), 2 deletions(-) (limited to 'include/hyperv') diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h index 1823a290a7b7..f9600f87186a 100644 --- a/include/hyperv/hvgdk_mini.h +++ b/include/hyperv/hvgdk_mini.h @@ -1533,4 +1533,10 @@ struct hv_mmio_write_input { u8 data[HV_HYPERCALL_MMIO_MAX_DATA_LENGTH]; } __packed; +enum hv_intercept_access_type { + HV_INTERCEPT_ACCESS_READ = 0, + HV_INTERCEPT_ACCESS_WRITE = 1, + HV_INTERCEPT_ACCESS_EXECUTE = 2 +}; + #endif /* _HV_HVGDK_MINI_H */ diff --git a/include/hyperv/hvhdk.h b/include/hyperv/hvhdk.h index 245f3db53bf1..5e83d3714966 100644 --- a/include/hyperv/hvhdk.h +++ b/include/hyperv/hvhdk.h @@ -779,7 +779,7 @@ struct hv_x64_intercept_message_header { u32 vp_index; u8 instruction_length:4; u8 cr8:4; /* Only set for exo partitions */ - u8 intercept_access_type; + u8 intercept_access_type; /* enum hv_intercept_access_type */ union hv_x64_vp_execution_state execution_state; struct hv_x64_segment_register cs_segment; u64 rip; @@ -825,7 +825,7 @@ union hv_arm64_vp_execution_state { struct hv_arm64_intercept_message_header { u32 vp_index; u8 instruction_length; - u8 intercept_access_type; + u8 intercept_access_type; /* enum hv_intercept_access_type */ union hv_arm64_vp_execution_state execution_state; u64 pc; u64 cpsr; -- cgit v1.2.3