[PATCH AUTOSEL 5.10 075/114] net: pktgen: fix access outside of user given buffer in pktgen_thread_write()

[Sasha Levin <sashal@kernel.org>]

From: Peter Seiderer <ps.report@gmx.net>

[ Upstream commit 425e64440ad0a2f03bdaf04be0ae53dededbaa77 ]

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@gmx.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250219084527.20488-8-ps.report@gmx.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 c2b3c454eddd9..57502e8628462 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -1770,8 +1770,8 @@ 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;
 
@@ -1801,7 +1801,8 @@ 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;
-- 
2.39.5