linux-kernel - [PATCH net-next v1 3/5] net: pktgen: fix access outside of user given buffer in pktgen_thread

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Message-ID: <20250117141613.691452-4-ps.report@gmx.net>
Date: Fri, 17 Jan 2025 15:16:11 +0100
From: Peter Seiderer <ps.report@....net>
To: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Shuah Khan <shuah@...nel.org>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Artem Chernyshev <artem.chernyshev@...-soft.ru>,
	Nam Cao <namcao@...utronix.de>,
	Peter Seiderer <ps.report@....net>
Subject: [PATCH net-next v1 3/5] net: pktgen: fix access outside of user given buffer in pktgen_thread_write()

Honour the user given buffer size for the strn_len() calls (otherwise
strn_len() will access memory outside of the user given buffer).

Signed-off-by: Peter Seiderer <ps.report@....net>
---
 net/core/pktgen.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 4f8ec6c9bed4..9536f9c4d9ef 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -1897,8 +1897,8 @@ static ssize_t pktgen_thread_write(struct file *file,
 	i = len;
 
 	/* Read variable name */
-
-	len = strn_len(&user_buffer[i], sizeof(name) - 1);
+	max = min(sizeof(name) - 1, count - i);
+	len = strn_len(&user_buffer[i], max);
 	if (len < 0)
 		return len;
 
@@ -1928,7 +1928,8 @@ static ssize_t pktgen_thread_write(struct file *file,
 	if (!strcmp(name, "add_device")) {
 		char f[32];
 		memset(f, 0, 32);
-		len = strn_len(&user_buffer[i], sizeof(f) - 1);
+		max = min(sizeof(f) - 1, count - i);
+		len = strn_len(&user_buffer[i], max);
 		if (len < 0) {
 			ret = len;
 			goto out;
-- 
2.48.0