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Subject[PATCH] EDAC, thunderx: fix possible out-of-bounds string access.
Date
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
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