linux-kernel - [PATCH 3/6] EDAC: fsl: Fix bad bit shift operations

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Message-Id: <20240709-imx95_edac-v1-3-3e9c146c1b01@nxp.com>
Date: Tue, 09 Jul 2024 16:23:04 -0400
From: Frank Li <Frank.Li@....com>
To: York Sun <york.sun@....com>, Borislav Petkov <bp@...en8.de>, 
 Tony Luck <tony.luck@...el.com>, James Morse <james.morse@....com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Robert Richter <rric@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, 
 Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Borislav Petkov <bp@...e.de>, devicetree@...r.kernel.org, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 Frank Li <Frank.Li@....com>, Priyanka Singh <priyanka.singh@....com>, 
 Sherry Sun <sherry.sun@....com>, Li Yang <leoyang.li@....com>
Subject: [PATCH 3/6] EDAC: fsl: Fix bad bit shift operations

From: Priyanka Singh <priyanka.singh@....com>

The original code:
	cap_high ^ (1 << (bad_data_bit - 32))

The variable bad_data_bit ranges from 0 to 63. If bad_data_bit is below 32,
bad_data_bit - 32 will be a negative value. Left shifting a negative
value in C is undefined behavior.

Fix this by checking the range of bad_data_bit.

Fixes: ea2eb9a8b620 ("EDAC, fsl-ddr: Separate FSL DDR driver from MPC85xx")
Signed-off-by: Priyanka Singh <priyanka.singh@....com>
Reviewed-by: Sherry Sun <sherry.sun@....com>
Signed-off-by: Li Yang <leoyang.li@....com>
Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/edac/fsl_ddr_edac.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/fsl_ddr_edac.c b/drivers/edac/fsl_ddr_edac.c
index 10b0a46669f3d..da743cf8a95e9 100644
--- a/drivers/edac/fsl_ddr_edac.c
+++ b/drivers/edac/fsl_ddr_edac.c
@@ -338,11 +338,18 @@ static void fsl_mc_check(struct mem_ctl_info *mci)
 			fsl_mc_printk(mci, KERN_ERR,
 				"Faulty ECC bit: %d\n", bad_ecc_bit);
 
-		fsl_mc_printk(mci, KERN_ERR,
-			"Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
-			cap_high ^ (1 << (bad_data_bit - 32)),
-			cap_low ^ (1 << bad_data_bit),
-			syndrome ^ (1 << bad_ecc_bit));
+		if ((bad_data_bit > 0 && bad_data_bit < 32) && bad_ecc_bit > 0) {
+			fsl_mc_printk(mci, KERN_ERR,
+				"Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
+				cap_high, cap_low ^ (1 << bad_data_bit),
+				syndrome ^ (1 << bad_ecc_bit));
+		}
+		if (bad_data_bit >= 32 && bad_ecc_bit > 0) {
+			fsl_mc_printk(mci, KERN_ERR,
+				"Expected Data / ECC:\t%#8.8x_%08x / %#2.2x\n",
+				cap_high ^ (1 << (bad_data_bit - 32)),
+				cap_low, syndrome ^ (1 << bad_ecc_bit));
+		}
 	}
 
 	fsl_mc_printk(mci, KERN_ERR,

-- 
2.34.1