6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
commit 17af420545a750f763025149fa7b833a4fc8b8f0 upstream.
syzbot reported a problem in ip6erspan_rcv() [1]
Issue is that ip6erspan_rcv() (and erspan_rcv()) no longer make
sure erspan_base_hdr is present in skb linear part (skb->head)
before getting @ver field from it.
Add the missing pskb_may_pull() calls.
v2: Reload iph pointer in erspan_rcv() after pskb_may_pull()
because skb->head might have changed.
[1]
BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2756 [inline]
BUG: KMSAN: uninit-value in ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
BUG: KMSAN: uninit-value in gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
pskb_may_pull_reason include/linux/skbuff.h:2742 [inline]
pskb_may_pull include/linux/skbuff.h:2756 [inline]
ip6erspan_rcv net/ipv6/ip6_gre.c:541 [inline]
gre_rcv+0x11f8/0x1930 net/ipv6/ip6_gre.c:610
ip6_protocol_deliver_rcu+0x1d4c/0x2ca0 net/ipv6/ip6_input.c:438
ip6_input_finish net/ipv6/ip6_input.c:483 [inline]
NF_HOOK include/linux/netfilter.h:314 [inline]
ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492
ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586
dst_input include/net/dst.h:460 [inline]
ip6_rcv_finish+0x955/0x970 net/ipv6/ip6_input.c:79
NF_HOOK include/linux/netfilter.h:314 [inline]
ipv6_rcv+0xde/0x390 net/ipv6/ip6_input.c:310
__netif_receive_skb_one_core net/core/dev.c:5538 [inline]
__netif_receive_skb+0x1da/0xa00 net/core/dev.c:5652
netif_receive_skb_internal net/core/dev.c:5738 [inline]
netif_receive_skb+0x58/0x660 net/core/dev.c:5798
tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1549
tun_get_user+0x5566/0x69e0 drivers/net/tun.c:2002
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2108 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xb63/0x1520 fs/read_write.c:590
ksys_write+0x20f/0x4c0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x93/0xe0 fs/read_write.c:652
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75
Uninit was created at:
slab_post_alloc_hook mm/slub.c:3804 [inline]
slab_alloc_node mm/slub.c:3845 [inline]
kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
__alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668
alloc_skb include/linux/skbuff.h:1318 [inline]
alloc_skb_with_frags+0xc8/0xbf0 net/core/skbuff.c:6504
sock_alloc_send_pskb+0xa81/0xbf0 net/core/sock.c:2795
tun_alloc_skb drivers/net/tun.c:1525 [inline]
tun_get_user+0x209a/0x69e0 drivers/net/tun.c:1846
tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
call_write_iter include/linux/fs.h:2108 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xb63/0x1520 fs/read_write.c:590
ksys_write+0x20f/0x4c0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x93/0xe0 fs/read_write.c:652
do_syscall_64+0xd5/0x1f0
entry_SYSCALL_64_after_hwframe+0x6d/0x75
CPU: 1 PID: 5045 Comm: syz-executor114 Not tainted 6.9.0-rc1-syzkaller-00021-g962490525cff #0
Fixes: cb73ee40b1b3 ("net: ip_gre: use erspan key field for tunnel lookup")
Reported-by: syzbot+1c1cf138518bf0c53d68@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/netdev/000000000000772f2c0614b66ef7@xxxxxxxxxx/
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240328112248.1101491-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/ip_gre.c | 5 +++++
net/ipv6/ip6_gre.c | 3 +++
2 files changed, 8 insertions(+)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -280,8 +280,13 @@ static int erspan_rcv(struct sk_buff *sk
tpi->flags | TUNNEL_NO_KEY,
iph->saddr, iph->daddr, 0);
} else {
+ if (unlikely(!pskb_may_pull(skb,
+ gre_hdr_len + sizeof(*ershdr))))
+ return PACKET_REJECT;
+
ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);
ver = ershdr->ver;
+ iph = ip_hdr(skb);
tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex,
tpi->flags | TUNNEL_KEY,
iph->saddr, iph->daddr, tpi->key);
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -528,6 +528,9 @@ static int ip6erspan_rcv(struct sk_buff
struct ip6_tnl *tunnel;
u8 ver;
+ if (unlikely(!pskb_may_pull(skb, sizeof(*ershdr))))
+ return PACKET_REJECT;
+
ipv6h = ipv6_hdr(skb);
ershdr = (struct erspan_base_hdr *)skb->data;
ver = ershdr->ver;
