From 0f63e656b1c679d32ac595de29d10c03efca6a25 Mon Sep 17 00:00:00 2001 From: "Kiryl Shutsemau (Meta)" Date: Mon, 13 Jul 2026 14:37:51 +0100 Subject: [PATCH] x86/tdx: Fix off-by-one in port I/O handling handle_in() and handle_out() in arch/x86/coco/tdx/tdx.c use: u64 mask = GENMASK(BITS_PER_BYTE * size, 0); GENMASK(h, l) includes bit h. For size=1 (INB), this produces GENMASK(8, 0) = 0x1FF (9 bits) instead of GENMASK(7, 0) = 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) Signed-off-by: Dave Hansen Reviewed-by: Kai Huang Reviewed-by: Kuppuswamy Sathyanarayanan Reviewed-by: Binbin Wu Reviewed-by: Rick Edgecombe Link: https://lore.kernel.org/all/CAKw_Dz96rfSQc6Rn+9QBcUFHhmkK+9zu+P=bxowfZwxrATCBRg@mail.gmail.com/ Cc:stable@vger.kernel.org Link: https://patch.msgid.link/20260713133753.223947-2-kirill@shutemov.name --- 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 29b6f1ed59ec..b8bbd715fb62 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -694,7 +694,7 @@ static bool handle_in(struct pt_regs *regs, int size, int port) .r13 = PORT_READ, .r14 = port, }; - u64 mask = GENMASK(BITS_PER_BYTE * size, 0); + u64 mask = GENMASK(BITS_PER_BYTE * size - 1, 0); bool success; /* @@ -714,7 +714,7 @@ static bool handle_in(struct pt_regs *regs, int size, int port) static bool handle_out(struct pt_regs *regs, int size, int port) { - u64 mask = GENMASK(BITS_PER_BYTE * size, 0); + u64 mask = GENMASK(BITS_PER_BYTE * size - 1, 0); /* * Emulate the I/O write via hypercall. More info about ABI can be found