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From:   Arnd Bergmann <arnd@kernel.org>
To:     Robert Richter <rric@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Tony Luck <tony.luck@intel.com>,
        Sergey Temerkhanov <s.temerkhanov@gmail.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        James Morse <james.morse@arm.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Yeqi Fu <asuk4.q@gmail.com>, linux-edac@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] EDAC, thunderx: fix possible out-of-bounds string access.
Date:   Wed, 22 Nov 2023 23:19:53 +0100
Message-Id: <20231122222007.3199885-1-arnd@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Arnd Bergmann <arnd@arndb.de>

Commit 1b56c90018f0 ("Makefile: Enable -Wstringop-overflow globally") exposes a
warning for a common bug in the usage of strncat():

drivers/edac/thunderx_edac.c: In function 'thunderx_ocx_com_threaded_isr':
drivers/edac/thunderx_edac.c:1136:17: error: 'strncat' specified bound 1024 equals destination size [-Werror=stringop-overflow=]
 1136 |                 strncat(msg, other, OCX_MESSAGE_SIZE);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/edac/thunderx_edac.c:1145:33: error: 'strncat' specified bound 1024 equals destination size [-Werror=stringop-overflow=]
 1145 |                                 strncat(msg, other, OCX_MESSAGE_SIZE);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/edac/thunderx_edac.c:1150:33: error: 'strncat' specified bound 1024 equals destination size [-Werror=stringop-overflow=]
 1150 |                                 strncat(msg, other, OCX_MESSAGE_SIZE);
      |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/edac/thunderx_edac.c: In function 'thunderx_l2c_threaded_isr':
drivers/edac/thunderx_edac.c:1899:17: error: 'strncat' specified bound 1024 equals destination size [-Werror=stringop-overflow=]
 1899 |                 strncat(msg, other, L2C_MESSAGE_SIZE);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/edac/thunderx_edac.c: In function 'thunderx_ocx_lnk_threaded_isr':
drivers/edac/thunderx_edac.c:1220:17: error: 'strncat' specified bound 1024 equals destination size [-Werror=stringop-overflow=]
 1220 |                 strncat(msg, other, OCX_MESSAGE_SIZE);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Apparently the author of this driver expected strncat() to behave the
way that strlcat() does, which uses the size of the destination buffer
as its third argument rather than the length of the source buffer.
The result is that there is no check on the size of the allocated
buffer.

Change it to use strncat().

Fixes: 41003396f932 ("EDAC, thunderx: Add Cavium ThunderX EDAC driver")
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/edac/thunderx_edac.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/thunderx_edac.c b/drivers/edac/thunderx_edac.c
index b9c5772da959..90d46e5c4ff0 100644
--- a/drivers/edac/thunderx_edac.c
+++ b/drivers/edac/thunderx_edac.c
@@ -1133,7 +1133,7 @@ static irqreturn_t thunderx_ocx_com_threaded_isr(int irq, void *irq_id)
 		decode_register(other, OCX_OTHER_SIZE,
 				ocx_com_errors, ctx->reg_com_int);
 
-		strncat(msg, other, OCX_MESSAGE_SIZE);
+		strlcat(msg, other, OCX_MESSAGE_SIZE);
 
 		for (lane = 0; lane < OCX_RX_LANES; lane++)
 			if (ctx->reg_com_int & BIT(lane)) {
@@ -1142,12 +1142,12 @@ static irqreturn_t thunderx_ocx_com_threaded_isr(int irq, void *irq_id)
 					 lane, ctx->reg_lane_int[lane],
 					 lane, ctx->reg_lane_stat11[lane]);
 
-				strncat(msg, other, OCX_MESSAGE_SIZE);
+				strlcat(msg, other, OCX_MESSAGE_SIZE);
 
 				decode_register(other, OCX_OTHER_SIZE,
 						ocx_lane_errors,
 						ctx->reg_lane_int[lane]);
-				strncat(msg, other, OCX_MESSAGE_SIZE);
+				strlcat(msg, other, OCX_MESSAGE_SIZE);
 			}
 
 		if (ctx->reg_com_int & OCX_COM_INT_CE)
@@ -1217,7 +1217,7 @@ static irqreturn_t thunderx_ocx_lnk_threaded_isr(int irq, void *irq_id)
 		decode_register(other, OCX_OTHER_SIZE,
 				ocx_com_link_errors, ctx->reg_com_link_int);
 
-		strncat(msg, other, OCX_MESSAGE_SIZE);
+		strlcat(msg, other, OCX_MESSAGE_SIZE);
 
 		if (ctx->reg_com_link_int & OCX_COM_LINK_INT_UE)
 			edac_device_handle_ue(ocx->edac_dev, 0, 0, msg);
@@ -1896,7 +1896,7 @@ static irqreturn_t thunderx_l2c_threaded_isr(int irq, void *irq_id)
 
 		decode_register(other, L2C_OTHER_SIZE, l2_errors, ctx->reg_int);
 
-		strncat(msg, other, L2C_MESSAGE_SIZE);
+		strlcat(msg, other, L2C_MESSAGE_SIZE);
 
 		if (ctx->reg_int & mask_ue)
 			edac_device_handle_ue(l2c->edac_dev, 0, 0, msg);
-- 
2.39.2