[PATCH v5 1/3] x86/tdx: Fix off-by-one in port I/O handling

[Kiryl Shutsemau]

From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>

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 <tsyrulnikov.borys@xxxxxxxxx>
Link: https://lore.kernel.org/all/CAKw_Dz96rfSQc6Rn+9QBcUFHhmkK+9zu+P=bxowfZwxrATCBRg@xxxxxxxxxxxxxx/
Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 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
-- 
2.54.0