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Peter Anvin" , Rick Edgecombe , Kuppuswamy Sathyanarayanan , Borys Tsyrulnikov , linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 1/2] x86/tdx: Fix off-by-one in port I/O handling Date: Tue, 31 Mar 2026 12:24:29 +0100 Message-ID: <20260331112430.71425-2-kas@kernel.org> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20260331112430.71425-1-kas@kernel.org> References: <20260331112430.71425-1-kas@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" handle_in() and handle_out() in arch/x86/coco/tdx/tdx.c use: u64 mask =3D GENMASK(BITS_PER_BYTE * size, 0); GENMASK(h, l) includes bit h. For size=3D1 (INB), this produces GENMASK(8, 0) =3D 0x1FF (9 bits) instead of GENMASK(7, 0) =3D 0xFF (8 bits). The mask is one bit too wide for all I/O sizes. Fix the mask calculation. Fixes: 03149948832a ("x86/tdx: Port I/O: Add runtime hypercalls") Reported-by: Borys Tsyrulnikov Signed-off-by: Kiryl Shutsemau (Meta) Cc: stable@vger.kernel.org Reviewed-by: Kai Huang Reviewed-by: Kuppuswamy Sathyanarayanan --- arch/x86/coco/tdx/tdx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index 7b2833705d47..4d7f71d50122 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -693,7 +693,7 @@ static bool handle_in(struct pt_regs *regs, int size, i= nt port) .r13 =3D PORT_READ, .r14 =3D port, }; - u64 mask =3D GENMASK(BITS_PER_BYTE * size, 0); + u64 mask =3D GENMASK(BITS_PER_BYTE * size - 1, 0); bool success; =20 /* @@ -713,7 +713,7 @@ static bool handle_in(struct pt_regs *regs, int size, i= nt port) =20 static bool handle_out(struct pt_regs *regs, int size, int port) { - u64 mask =3D GENMASK(BITS_PER_BYTE * size, 0); + u64 mask =3D GENMASK(BITS_PER_BYTE * size - 1, 0); =20 /* * Emulate the I/O write via hypercall. More info about ABI can be found --=20 2.51.2