netlink: rate-limit leftover bytes warning and print process name

[ Upstream commit bfc5184b ]

Any process is able to send netlink messages with leftover bytes.
Make the warning rate-limited to prevent too much log spam.

The warning is supposed to help find userspace bugs, so print the
triggering command name to implicate the buggy program.

[v2: Use pr_warn_ratelimited instead of printk_ratelimited.]
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Add #include of <linux/sched.h> for definition of struct task_struct,
 as in 3.2 it doesn't get included indirectly on all architectures.  Thanks
 to Guenter Roeck for debugging this.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

lib/nlattr.c

@@ -12,6 +12,8 @@
 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
 #include <linux/string.h>
+#include <linux/ratelimit.h>
+#include <linux/sched.h>
 #include <linux/types.h>
 #include <net/netlink.h>
 
@@ -197,8 +199,8 @@ int nla_parse(struct nlattr **tb, int maxtype, const struct nlattr *head,
 	}
 
 	if (unlikely(rem > 0))
-		printk(KERN_WARNING "netlink: %d bytes leftover after parsing "
-		       "attributes.\n", rem);
+		pr_warn_ratelimited("netlink: %d bytes leftover after parsing attributes in process `%s'.\n",
+				    rem, current->comm);
 
 	err = 0;
 errout: