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Date: Sat, 21 Oct 2023 19:06:34 +0200
From: Christophe JAILLET <>
	Robert Richter <>,
	Borislav Petkov <>,
	Tony Luck <>,
	James Morse <>,
	Mauro Carvalho Chehab <>,
	Sergey Temerkhanov <>
	Christophe JAILLET <>,
	Borislav Petkov <>,
Subject: [PATCH] EDAC/thunderx: Fix some potential buffer overflow in thunderx_ocx_com_threaded_isr()

strncat() usage in thunderx_ocx_com_threaded_isr() is wrong.
The size given to strncat() is the maximum number of bytes that can be
written, excluding the trailing NULL.

Here, the size of the 'msg' buffer is used (i.e. OCX_MESSAGE_SIZE), not
the space that is remaining.
The space for the ending NULL is also not taken into account.

in order to fix it:
   - call decode_register() before the snprintf() calls
   - use scnprintf() instead of snprintf() and compute, in the 'remaining'
     variable, the space that is still available in the 'msg' buffer
   - add a %s at the end of the format strings and append directly the
     result of decode_register() stored in 'other'
   - write directly at the right position in the 'msg' buffer when
     appending some data in the for loop.

Doing so, all usages of strncat() are removed.

Fixes: 41003396f932 ("EDAC, thunderx: Add Cavium ThunderX EDAC driver")
Signed-off-by: Christophe JAILLET <>
This is cross-compile tested only.
Review with care.
 drivers/edac/thunderx_edac.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/edac/thunderx_edac.c b/drivers/edac/thunderx_edac.c
index b9c5772da959..9544836dbd19 100644
--- a/drivers/edac/thunderx_edac.c
+++ b/drivers/edac/thunderx_edac.c
@@ -1111,6 +1111,7 @@ static irqreturn_t thunderx_ocx_com_threaded_isr(int irq, void *irq_id)
 	unsigned long tail;
 	struct ocx_com_err_ctx *ctx;
+	size_t remaining;
 	int lane;
 	char *msg;
 	char *other;
@@ -1127,27 +1128,26 @@ static irqreturn_t thunderx_ocx_com_threaded_isr(int irq, void *irq_id)
 		ctx = &ocx->com_err_ctx[tail];
-		snprintf(msg, OCX_MESSAGE_SIZE, "%s: OCX_COM_INT: %016llx",
-			ocx->edac_dev->ctl_name, ctx->reg_com_int);
 		decode_register(other, OCX_OTHER_SIZE,
 				ocx_com_errors, ctx->reg_com_int);
-		strncat(msg, other, OCX_MESSAGE_SIZE);
+		remaining = OCX_MESSAGE_SIZE;
+		remaining -= scnprintf(msg, remaining, "%s: OCX_COM_INT: %016llx%s",
+				       ocx->edac_dev->ctl_name, ctx->reg_com_int,
+				       other);
 		for (lane = 0; lane < OCX_RX_LANES; lane++)
 			if (ctx->reg_com_int & BIT(lane)) {
-				snprintf(other, OCX_OTHER_SIZE,
-					 "\n\tOCX_LNE_INT[%02d]: %016llx OCX_LNE_STAT11[%02d]: %016llx",
-					 lane, ctx->reg_lane_int[lane],
-					 lane, ctx->reg_lane_stat11[lane]);
-				strncat(msg, other, OCX_MESSAGE_SIZE);
 				decode_register(other, OCX_OTHER_SIZE,
-				strncat(msg, other, OCX_MESSAGE_SIZE);
+				remaining -= scnprintf(msg + (OCX_MESSAGE_SIZE - remaining),
+						       remaining,
+						       "\n\tOCX_LNE_INT[%02d]: %016llx OCX_LNE_STAT11[%02d]: %016llx%s",
+						       lane, ctx->reg_lane_int[lane],
+						       lane, ctx->reg_lane_stat11[lane],
+						       other);
 		if (ctx->reg_com_int & OCX_COM_INT_CE)

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