linux-kernel - [PATCH] s390/cmm: Replace sprintf with scnprintf for buffer safety

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Message-ID: <20251001163622.164143-1-hi@josie.lol>
Date: Wed,  1 Oct 2025 18:36:22 +0200
From: Josephine Pfeiffer <hi@...ie.lol>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] s390/cmm: Replace sprintf with scnprintf for buffer safety

Replace sprintf() with scnprintf() in cmm_timeout_handler() to prevent
potential buffer overflow. The scnprintf() function ensures we don't
write beyond the buffer size and provides safer string formatting.

Signed-off-by: Josephine Pfeiffer <hi@...ie.lol>
---
 arch/s390/mm/cmm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c
index e2a6eb92420f..eb7ef63fab1e 100644
--- a/arch/s390/mm/cmm.c
+++ b/arch/s390/mm/cmm.c
@@ -321,8 +321,8 @@ static int cmm_timeout_handler(const struct ctl_table *ctl, int write,
 		cmm_set_timeout(nr, seconds);
 		*ppos += *lenp;
 	} else {
-		len = sprintf(buf, "%ld %ld\n",
-			      cmm_timeout_pages, cmm_timeout_seconds);
+		len = scnprintf(buf, sizeof(buf), "%ld %ld\n",
+				cmm_timeout_pages, cmm_timeout_seconds);
 		if (len > *lenp)
 			len = *lenp;
 		memcpy(buffer, buf, len);
-- 
2.51.0