linux-kernel - [PATCH net-next v1 1/2] net: pktgen: add strict buffer parsing index check

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Message-ID: <20250317090401.1240704-1-ps.report@gmx.net>
Date: Mon, 17 Mar 2025 10:04:00 +0100
From: Peter Seiderer <ps.report@....net>
To: netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...aro.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>,
	Peter Seiderer <ps.report@....net>
Subject: [PATCH net-next v1 1/2] net: pktgen: add strict buffer parsing index check

Add strict buffer parsing index check to avoid the following Smatch
warning:

  net/core/pktgen.c:877 get_imix_entries()
  warn: check that incremented offset 'i' is capped

Checking the buffer index i after every get_user/i++ step and returning
with error code immediately avoids the current indirect (but correct)
error handling.

Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/netdev/36cf3ee2-38b1-47e5-a42a-363efeb0ace3@stanley.mountain/
Signed-off-by: Peter Seiderer <ps.report@....net>
---
 net/core/pktgen.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index e850598db3e7..fe7fdefab994 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -856,6 +856,9 @@ static ssize_t get_imix_entries(const char __user *buffer,
 		if (pkt_dev->n_imix_entries >= MAX_IMIX_ENTRIES)
 			return -E2BIG;
 
+		if (i >= maxlen)
+			return -EINVAL;
+
 		max = min(10, maxlen - i);
 		len = num_arg(&buffer[i], max, &size);
 		if (len < 0)
@@ -869,6 +872,8 @@ static ssize_t get_imix_entries(const char __user *buffer,
 		if (c != ',')
 			return -EINVAL;
 		i++;
+		if (i >= maxlen)
+			return -EINVAL;
 
 		if (size < 14 + 20 + 8)
 			size = 14 + 20 + 8;
@@ -911,6 +916,9 @@ static ssize_t get_labels(const char __user *buffer,
 		if (n >= MAX_MPLS_LABELS)
 			return -E2BIG;
 
+		if (i >= maxlen)
+			return -EINVAL;
+
 		max = min(8, maxlen - i);
 		len = hex32_arg(&buffer[i], max, &tmp);
 		if (len < 0)
-- 
2.48.1