--- /dev/null
+From 3a3be7ff9224f424e485287b54be00d2c6bd9c40 Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <edumazet@google.com>
+Date: Thu, 8 Aug 2024 13:24:55 +0000
+Subject: gtp: pull network headers in gtp_dev_xmit()
+
+From: Eric Dumazet <edumazet@google.com>
+
+commit 3a3be7ff9224f424e485287b54be00d2c6bd9c40 upstream.
+
+syzbot/KMSAN reported use of uninit-value in get_dev_xmit() [1]
+
+We must make sure the IPv4 or Ipv6 header is pulled in skb->head
+before accessing fields in them.
+
+Use pskb_inet_may_pull() to fix this issue.
+
+[1]
+BUG: KMSAN: uninit-value in ipv6_pdp_find drivers/net/gtp.c:220 [inline]
+ BUG: KMSAN: uninit-value in gtp_build_skb_ip6 drivers/net/gtp.c:1229 [inline]
+ BUG: KMSAN: uninit-value in gtp_dev_xmit+0x1424/0x2540 drivers/net/gtp.c:1281
+ ipv6_pdp_find drivers/net/gtp.c:220 [inline]
+ gtp_build_skb_ip6 drivers/net/gtp.c:1229 [inline]
+ gtp_dev_xmit+0x1424/0x2540 drivers/net/gtp.c:1281
+ __netdev_start_xmit include/linux/netdevice.h:4913 [inline]
+ netdev_start_xmit include/linux/netdevice.h:4922 [inline]
+ xmit_one net/core/dev.c:3580 [inline]
+ dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3596
+ __dev_queue_xmit+0x358c/0x5610 net/core/dev.c:4423
+ dev_queue_xmit include/linux/netdevice.h:3105 [inline]
+ packet_xmit+0x9c/0x6c0 net/packet/af_packet.c:276
+ packet_snd net/packet/af_packet.c:3145 [inline]
+ packet_sendmsg+0x90e3/0xa3a0 net/packet/af_packet.c:3177
+ sock_sendmsg_nosec net/socket.c:730 [inline]
+ __sock_sendmsg+0x30f/0x380 net/socket.c:745
+ __sys_sendto+0x685/0x830 net/socket.c:2204
+ __do_sys_sendto net/socket.c:2216 [inline]
+ __se_sys_sendto net/socket.c:2212 [inline]
+ __x64_sys_sendto+0x125/0x1d0 net/socket.c:2212
+ x64_sys_call+0x3799/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:45
+ do_syscall_x64 arch/x86/entry/common.c:52 [inline]
+ do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
+ entry_SYSCALL_64_after_hwframe+0x77/0x7f
+
+Uninit was created at:
+ slab_post_alloc_hook mm/slub.c:3994 [inline]
+ slab_alloc_node mm/slub.c:4037 [inline]
+ kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4080
+ kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:583
+ __alloc_skb+0x363/0x7b0 net/core/skbuff.c:674
+ alloc_skb include/linux/skbuff.h:1320 [inline]
+ alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6526
+ sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2815
+ packet_alloc_skb net/packet/af_packet.c:2994 [inline]
+ packet_snd net/packet/af_packet.c:3088 [inline]
+ packet_sendmsg+0x749c/0xa3a0 net/packet/af_packet.c:3177
+ sock_sendmsg_nosec net/socket.c:730 [inline]
+ __sock_sendmsg+0x30f/0x380 net/socket.c:745
+ __sys_sendto+0x685/0x830 net/socket.c:2204
+ __do_sys_sendto net/socket.c:2216 [inline]
+ __se_sys_sendto net/socket.c:2212 [inline]
+ __x64_sys_sendto+0x125/0x1d0 net/socket.c:2212
+ x64_sys_call+0x3799/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:45
+ do_syscall_x64 arch/x86/entry/common.c:52 [inline]
+ do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
+ entry_SYSCALL_64_after_hwframe+0x77/0x7f
+
+CPU: 0 UID: 0 PID: 7115 Comm: syz.1.515 Not tainted 6.11.0-rc1-syzkaller-00043-g94ede2a3e913 #0
+Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
+
+Fixes: 999cb275c807 ("gtp: add IPv6 support")
+Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Cc: Harald Welte <laforge@gnumonks.org>
+Reviewed-by: Pablo Neira Ayuso <pablo@netfilter.org>
+Link: https://patch.msgid.link/20240808132455.3413916-1-edumazet@google.com
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/net/gtp.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/drivers/net/gtp.c
++++ b/drivers/net/gtp.c
+@@ -567,6 +567,9 @@ static netdev_tx_t gtp_dev_xmit(struct s
+ if (skb_cow_head(skb, dev->needed_headroom))
+ goto tx_err;
+
++ if (!pskb_inet_may_pull(skb))
++ goto tx_err;
++
+ skb_reset_inner_headers(skb);
+
+ /* PDP context lookups in gtp_build_skb_*() need rcu read-side lock. */