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@linaro.org>
Closes: https://lore.kernel.org/netdev/36cf3ee2-38b1-47e5-a42a-363efeb0ace3@stanley.mountain/
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250317090401.1240704-1-ps.report@gmx.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index e850598db3e70331c0588bd4b287b589721273fc..fe7fdefab994c3bd0b9ab73fce6ac47fff30a9db 100644 (file)
--- 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)