From: Sean Christopherson Date: Fri, 8 Aug 2025 17:23:57 +0000 (-0700) Subject: x86/umip: Fix decoding of register forms of 0F 01 (SGDT and SIDT aliases) X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=27b1fd62012dfe9d3eb8ecde344d7aa673695ecf;p=thirdparty%2Fkernel%2Fstable.git x86/umip: Fix decoding of register forms of 0F 01 (SGDT and SIDT aliases) Filter out the register forms of 0F 01 when determining whether or not to emulate in response to a potential UMIP violation #GP, as SGDT and SIDT only accept memory operands. The register variants of 0F 01 are used to encode instructions for things like VMX and SGX, i.e. not checking the Mod field would cause the kernel to incorrectly emulate on #GP, e.g. due to a CPL violation on VMLAUNCH. Fixes: 1e5db223696a ("x86/umip: Add emulation code for UMIP instructions") Signed-off-by: Sean Christopherson Signed-off-by: Borislav Petkov (AMD) Acked-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org --- diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c index 406ac01ce16dc..d432f3824f0c2 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -163,8 +163,19 @@ static int identify_insn(struct insn *insn) if (insn->opcode.bytes[1] == 0x1) { switch (X86_MODRM_REG(insn->modrm.value)) { case 0: + /* The reg form of 0F 01 /0 encodes VMX instructions. */ + if (X86_MODRM_MOD(insn->modrm.value) == 3) + return -EINVAL; + return UMIP_INST_SGDT; case 1: + /* + * The reg form of 0F 01 /1 encodes MONITOR/MWAIT, + * STAC/CLAC, and ENCLS. + */ + if (X86_MODRM_MOD(insn->modrm.value) == 3) + return -EINVAL; + return UMIP_INST_SIDT; case 4: return UMIP_INST_SMSW;