udplite: Print deprecation notice.

Recently syzkaller reported a 7-year-old null-ptr-deref [0] that occurs
when a UDP-Lite socket tries to allocate a buffer under memory pressure.

Someone should have stumbled on the bug much earlier if UDP-Lite had been
used in a real app.  Also, we do not always need a large UDP-Lite workload
to hit the bug since UDP and UDP-Lite share the same memory accounting
limit.

Removing UDP-Lite would simplify UDP code removing a bunch of conditionals
in fast path.

Let's add a deprecation notice when UDP-Lite socket is created and schedule
its removal to 2025.

Link: https://lore.kernel.org/netdev/20230523163305.66466-1-kuniyu@amazon.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/udplite.c b/net/ipv4/udplite.c
index 56d94d2..143f93a 100644 (file)
--- a/net/ipv4/udplite.c
+++ b/net/ipv4/udplite.c
@@ -22,6 +22,8 @@ static int udplite_sk_init(struct sock *sk)
 {
        udp_init_sock(sk);
        udp_sk(sk)->pcflag = UDPLITE_BIT;
+       pr_warn_once("UDP-Lite is deprecated and scheduled to be removed in 2025, "
+                    "please contact the netdev mailing list\n");
        return 0;
 }
 

diff --git a/net/ipv6/udplite.c b/net/ipv6/udplite.c
index 3bab0cc..8e010d0 100644 (file)
--- a/net/ipv6/udplite.c
+++ b/net/ipv6/udplite.c
@@ -8,6 +8,8 @@
  *  Changes:
  *  Fixes:
  */
+#define pr_fmt(fmt) "UDPLite6: " fmt
+
 #include <linux/export.h>
 #include <linux/proc_fs.h>
 #include "udp_impl.h"
@@ -16,6 +18,8 @@ static int udplitev6_sk_init(struct sock *sk)
 {
        udpv6_init_sock(sk);
        udp_sk(sk)->pcflag = UDPLITE_BIT;
+       pr_warn_once("UDP-Lite is deprecated and scheduled to be removed in 2025, "
+                    "please contact the netdev mailing list\n");
        return 0;
 }