KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O When completing emulation of instruction that generated a userspace exit for I/O, don't recheck L1 intercepts as KVM has already finished that phase of instruction execution, i.e. has already committed to allowing L2 to perform I/O. If L1 (or host userspace) modifies the I/O permission bitmaps during the exit to userspace, KVM will treat the access as being intercepted despite already having emulated the I/O access. Pivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation. Of the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the intended "recipient") can reach the code in question. gp_interception()'s use is mutually exclusive with is_guest_mode(), and complete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with EMULTYPE_SKIP. The bad behavior was detected by a syzkaller program that toggles port I/O interception during the userspace I/O exit, ultimately resulting in a WARN on vcpu->arch.pio.count being non-zero due to KVM no completing emulation of the I/O instruction. WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm] Modules linked in: kvm_intel kvm irqbypass CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:emulator_pio_in_out+
CVE-2025-40026
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-40026
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "a908eca437789589dd4624da428614c1275064dc",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "00338255bb1f422642fb2798ebe92e93b6e4209b",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "e0ce3ed1048a47986d15aef1a98ebda25560d257",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "ba35a5d775799ce5ad60230be97336f2fefd518e",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "3d3abf3f7e8b1abb082070a343de82d7efc80523",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "e7177c7e32cb806f348387b7f4faafd4a5b32054",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "3a062a5c55adc5507600b9ae6d911e247e2f1d6e",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "7366830642505683bbe905a2ba5d18d6e4b512b8",
"versionType": "git"
},
{
"status": "affected",
"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9",
"lessThan": "e750f85391286a4c8100275516973324b621a269",
"versionType": "git"
}
],
"programFiles": [
"arch/x86/kvm/emulate.c",
"arch/x86/kvm/kvm_emulate.h",
"arch/x86/kvm/x86.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.4.301",
"versionType": "semver",
"lessThanOrEqual": "5.4.*"
},
{
"status": "unaffected",
"version": "5.10.246",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.195",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.157",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.111",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.52",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.16.12",
"versionType": "semver",
"lessThanOrEqual": "6.16.*"
},
{
"status": "unaffected",
"version": "6.17.2",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"arch/x86/kvm/emulate.c",
"arch/x86/kvm/kvm_emulate.h",
"arch/x86/kvm/x86.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-40026
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #30662 · Revision 1
- Added to Heist Feed
- Publisher date