TLDRVuln - Cybersecurity Vulnerabilities Made Simple

In the Linux kernel, the following vulnerability has been resolved:

ip6_tunnel: make sure to pull inner header in __ip6_tnl_rcv()

syzbot found __ip6_tnl_rcv() could access unitiliazed data [1].

Call pskb_inet_may_pull() to fix this, and initialize ipv6h

variable after this call as it can change skb->head.

[1]

BUG: KMSAN: uninit-value in __INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]

BUG: KMSAN: uninit-value in INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]

BUG: KMSAN: uninit-value in IP6_ECN_decapsulate+0x7df/0x1e50 include/net/inet_ecn.h:321

__INET_ECN_decapsulate include/net/inet_ecn.h:253 [inline]

INET_ECN_decapsulate include/net/inet_ecn.h:275 [inline]

IP6_ECN_decapsulate+0x7df/0x1e50 include/net/inet_ecn.h:321

ip6ip6_dscp_ecn_decapsulate+0x178/0x1b0 net/ipv6/ip6_tunnel.c:727

__ip6_tnl_rcv+0xd4e/0x1590 net/ipv6/ip6_tunnel.c:845

ip6_tnl_rcv+0xce/0x100 net/ipv6/ip6_tunnel.c:888

gre_rcv+0x143f/0x1870

ip6_protocol_deliver_rcu+0xda6/0x2a60 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:461 [inline]

ip6_rcv_finish+0x5db/0x870 net/ipv6/ip6_input.c:79

NF_HOOK include/linux/netfilter.h:314 [inline]

ipv6_rcv+0xda/0x390 net/ipv6/ip6_input.c:310

__netif_receive_skb_one_core net/core/dev.c:5532 [inline]

__netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5646

netif_receive_skb_internal net/core/dev.c:5732 [inline]

netif_receive_skb+0x58/0x660 net/core/dev.c:5791

tun_rx_batched+0x3ee/0x980 drivers/net/tun.c:1555

tun_get_user+0x53af/0x66d0 drivers/net/tun.c:2002

tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048

call_write_iter include/linux/fs.h:2084 [inline]

new_sync_write fs/read_write.c:497 [inline]

vfs_write+0x786/0x1200 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+0x93/0xd0 fs/read_write.c:652

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:

slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768

slab_alloc_node mm/slub.c:3478 [inline]

kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523

kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560

__alloc_skb+0x318/0x740 net/core/skbuff.c:651

alloc_skb include/linux/skbuff.h:1286 [inline]

alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6334

sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2787

tun_alloc_skb drivers/net/tun.c:1531 [inline]

tun_get_user+0x1e8a/0x66d0 drivers/net/tun.c:1846