From: Eric Dumazet edumazet@google.com
[ Upstream commit 02c71b144c811bcdd865e0a1226d0407d11357e8 ]
syzbot recently found a way to crash the kernel [1]
Issue here is that inet_hash() & inet_unhash() are currently only meant to be used by TCP & DCCP, since only these protocols provide the needed hashinfo pointer.
L2TP uses a single list (instead of a hash table)
This old bug became an issue after commit 610236587600 ("bpf: Add new cgroup attach type to enable sock modifications") since after this commit, sk_common_release() can be called while the L2TP socket is still considered 'hashed'.
general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] CPU: 0 PID: 7063 Comm: syz-executor654 Not tainted 5.7.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:inet_unhash+0x11f/0x770 net/ipv4/inet_hashtables.c:600 Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e dd 04 00 00 48 8d 7d 08 44 8b 73 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 55 05 00 00 48 8d 7d 14 4c 8b 6d 08 48 b8 00 00 RSP: 0018:ffffc90001777d30 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffff88809a6df940 RCX: ffffffff8697c242 RDX: 0000000000000001 RSI: ffffffff8697c251 RDI: 0000000000000008 RBP: 0000000000000000 R08: ffff88809f3ae1c0 R09: fffffbfff1514cc1 R10: ffffffff8a8a6607 R11: fffffbfff1514cc0 R12: ffff88809a6df9b0 R13: 0000000000000007 R14: 0000000000000000 R15: ffffffff873a4d00 FS: 0000000001d2b880(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006cd090 CR3: 000000009403a000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: sk_common_release+0xba/0x370 net/core/sock.c:3210 inet_create net/ipv4/af_inet.c:390 [inline] inet_create+0x966/0xe00 net/ipv4/af_inet.c:248 __sock_create+0x3cb/0x730 net/socket.c:1428 sock_create net/socket.c:1479 [inline] __sys_socket+0xef/0x200 net/socket.c:1521 __do_sys_socket net/socket.c:1530 [inline] __se_sys_socket net/socket.c:1528 [inline] __x64_sys_socket+0x6f/0xb0 net/socket.c:1528 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x441e29 Code: e8 fc b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffdce184148 EFLAGS: 00000246 ORIG_RAX: 0000000000000029 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441e29 RDX: 0000000000000073 RSI: 0000000000000002 RDI: 0000000000000002 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000402c30 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: ---[ end trace 23b6578228ce553e ]--- RIP: 0010:inet_unhash+0x11f/0x770 net/ipv4/inet_hashtables.c:600 Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e dd 04 00 00 48 8d 7d 08 44 8b 73 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 55 05 00 00 48 8d 7d 14 4c 8b 6d 08 48 b8 00 00 RSP: 0018:ffffc90001777d30 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: ffff88809a6df940 RCX: ffffffff8697c242 RDX: 0000000000000001 RSI: ffffffff8697c251 RDI: 0000000000000008 RBP: 0000000000000000 R08: ffff88809f3ae1c0 R09: fffffbfff1514cc1 R10: ffffffff8a8a6607 R11: fffffbfff1514cc0 R12: ffff88809a6df9b0 R13: 0000000000000007 R14: 0000000000000000 R15: ffffffff873a4d00 FS: 0000000001d2b880(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006cd090 CR3: 000000009403a000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Fixes: 0d76751fad77 ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support") Signed-off-by: Eric Dumazet edumazet@google.com Cc: James Chapman jchapman@katalix.com Cc: Andrii Nakryiko andriin@fb.com Reported-by: syzbot+3610d489778b57cc8031@syzkaller.appspotmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/l2tp/l2tp_ip.c | 29 ++++++++++++++++++++++------- net/l2tp/l2tp_ip6.c | 30 ++++++++++++++++++++++-------- 2 files changed, 44 insertions(+), 15 deletions(-)
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c index d4c60523c549..99881b81f302 100644 --- a/net/l2tp/l2tp_ip.c +++ b/net/l2tp/l2tp_ip.c @@ -24,7 +24,6 @@ #include <net/icmp.h> #include <net/udp.h> #include <net/inet_common.h> -#include <net/inet_hashtables.h> #include <net/tcp_states.h> #include <net/protocol.h> #include <net/xfrm.h> @@ -213,15 +212,31 @@ static int l2tp_ip_recv(struct sk_buff *skb) return 0; }
-static int l2tp_ip_open(struct sock *sk) +static int l2tp_ip_hash(struct sock *sk) { - /* Prevent autobind. We don't have ports. */ - inet_sk(sk)->inet_num = IPPROTO_L2TP; + if (sk_unhashed(sk)) { + write_lock_bh(&l2tp_ip_lock); + sk_add_node(sk, &l2tp_ip_table); + write_unlock_bh(&l2tp_ip_lock); + } + return 0; +}
+static void l2tp_ip_unhash(struct sock *sk) +{ + if (sk_unhashed(sk)) + return; write_lock_bh(&l2tp_ip_lock); - sk_add_node(sk, &l2tp_ip_table); + sk_del_node_init(sk); write_unlock_bh(&l2tp_ip_lock); +} + +static int l2tp_ip_open(struct sock *sk) +{ + /* Prevent autobind. We don't have ports. */ + inet_sk(sk)->inet_num = IPPROTO_L2TP;
+ l2tp_ip_hash(sk); return 0; }
@@ -598,8 +613,8 @@ static struct proto l2tp_ip_prot = { .sendmsg = l2tp_ip_sendmsg, .recvmsg = l2tp_ip_recvmsg, .backlog_rcv = l2tp_ip_backlog_recv, - .hash = inet_hash, - .unhash = inet_unhash, + .hash = l2tp_ip_hash, + .unhash = l2tp_ip_unhash, .obj_size = sizeof(struct l2tp_ip_sock), #ifdef CONFIG_COMPAT .compat_setsockopt = compat_ip_setsockopt, diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c index 2f28f9910b92..2ff25c445b82 100644 --- a/net/l2tp/l2tp_ip6.c +++ b/net/l2tp/l2tp_ip6.c @@ -24,8 +24,6 @@ #include <net/icmp.h> #include <net/udp.h> #include <net/inet_common.h> -#include <net/inet_hashtables.h> -#include <net/inet6_hashtables.h> #include <net/tcp_states.h> #include <net/protocol.h> #include <net/xfrm.h> @@ -226,15 +224,31 @@ static int l2tp_ip6_recv(struct sk_buff *skb) return 0; }
-static int l2tp_ip6_open(struct sock *sk) +static int l2tp_ip6_hash(struct sock *sk) { - /* Prevent autobind. We don't have ports. */ - inet_sk(sk)->inet_num = IPPROTO_L2TP; + if (sk_unhashed(sk)) { + write_lock_bh(&l2tp_ip6_lock); + sk_add_node(sk, &l2tp_ip6_table); + write_unlock_bh(&l2tp_ip6_lock); + } + return 0; +}
+static void l2tp_ip6_unhash(struct sock *sk) +{ + if (sk_unhashed(sk)) + return; write_lock_bh(&l2tp_ip6_lock); - sk_add_node(sk, &l2tp_ip6_table); + sk_del_node_init(sk); write_unlock_bh(&l2tp_ip6_lock); +} + +static int l2tp_ip6_open(struct sock *sk) +{ + /* Prevent autobind. We don't have ports. */ + inet_sk(sk)->inet_num = IPPROTO_L2TP;
+ l2tp_ip6_hash(sk); return 0; }
@@ -732,8 +746,8 @@ static struct proto l2tp_ip6_prot = { .sendmsg = l2tp_ip6_sendmsg, .recvmsg = l2tp_ip6_recvmsg, .backlog_rcv = l2tp_ip6_backlog_recv, - .hash = inet6_hash, - .unhash = inet_unhash, + .hash = l2tp_ip6_hash, + .unhash = l2tp_ip6_unhash, .obj_size = sizeof(struct l2tp_ip6_sock), #ifdef CONFIG_COMPAT .compat_setsockopt = compat_ipv6_setsockopt,