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Message-ID: <CADvbK_dhcQGtBtutCuwiKhjZ-Lw1Oxc15d1CrHs4Tf7r5keB0A@mail.gmail.com>
Date: Thu, 7 Nov 2024 16:08:27 -0500
From: Xin Long <lucien.xin@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net-next] sctp: fix possible UAF in sctp_v6_available()
On Thu, Nov 7, 2024 at 2:20 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> A lockdep report [1] with CONFIG_PROVE_RCU_LIST=y hints
> that sctp_v6_available() is calling dev_get_by_index_rcu()
> and ipv6_chk_addr() without holding rcu.
>
> [1]
> =============================
> WARNING: suspicious RCU usage
> 6.12.0-rc5-virtme #1216 Tainted: G W
> -----------------------------
> net/core/dev.c:876 RCU-list traversed in non-reader section!!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 1 lock held by sctp_hello/31495:
> #0: ffff9f1ebbdb7418 (sk_lock-AF_INET6){+.+.}-{0:0}, at: sctp_bind (./arch/x86/include/asm/jump_label.h:27 net/sctp/socket.c:315) sctp
>
> stack backtrace:
> CPU: 7 UID: 0 PID: 31495 Comm: sctp_hello Tainted: G W 6.12.0-rc5-virtme #1216
> Tainted: [W]=WARN
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl (lib/dump_stack.c:123)
> lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822)
> dev_get_by_index_rcu (net/core/dev.c:876 (discriminator 7))
> sctp_v6_available (net/sctp/ipv6.c:701) sctp
> sctp_do_bind (net/sctp/socket.c:400 (discriminator 1)) sctp
> sctp_bind (net/sctp/socket.c:320) sctp
> inet6_bind_sk (net/ipv6/af_inet6.c:465)
> ? security_socket_bind (security/security.c:4581 (discriminator 1))
> __sys_bind (net/socket.c:1848 net/socket.c:1869)
> ? do_user_addr_fault (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 ./include/linux/mm.h:729 arch/x86/mm/fault.c:1340)
> ? do_user_addr_fault (./arch/x86/include/asm/preempt.h:84 (discriminator 13) ./include/linux/rcupdate.h:98 (discriminator 13) ./include/linux/rcupdate.h:882 (discriminator 13) ./include/linux/mm.h:729 (discriminator 13) arch/x86/mm/fault.c:1340 (discriminator 13))
> __x64_sys_bind (net/socket.c:1877 (discriminator 1) net/socket.c:1875 (discriminator 1) net/socket.c:1875 (discriminator 1))
> do_syscall_64 (arch/x86/entry/common.c:52 (discriminator 1) arch/x86/entry/common.c:83 (discriminator 1))
> entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
> RIP: 0033:0x7f59b934a1e7
> Code: 44 00 00 48 8b 15 39 8c 0c 00 f7 d8 64 89 02 b8 ff ff ff ff eb bd 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 b8 31 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 09 8c 0c 00 f7 d8 64 89 01 48
> All code
> ========
> 0: 44 00 00 add %r8b,(%rax)
> 3: 48 8b 15 39 8c 0c 00 mov 0xc8c39(%rip),%rdx # 0xc8c43
> a: f7 d8 neg %eax
> c: 64 89 02 mov %eax,%fs:(%rdx)
> f: b8 ff ff ff ff mov $0xffffffff,%eax
> 14: eb bd jmp 0xffffffffffffffd3
> 16: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
> 1d: 00 00 00
> 20: 0f 1f 00 nopl (%rax)
> 23: b8 31 00 00 00 mov $0x31,%eax
> 28: 0f 05 syscall
> 2a:* 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction
> 30: 73 01 jae 0x33
> 32: c3 ret
> 33: 48 8b 0d 09 8c 0c 00 mov 0xc8c09(%rip),%rcx # 0xc8c43
> 3a: f7 d8 neg %eax
> 3c: 64 89 01 mov %eax,%fs:(%rcx)
> 3f: 48 rex.W
>
> Code starting with the faulting instruction
> ===========================================
> 0: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax
> 6: 73 01 jae 0x9
> 8: c3 ret
> 9: 48 8b 0d 09 8c 0c 00 mov 0xc8c09(%rip),%rcx # 0xc8c19
> 10: f7 d8 neg %eax
> 12: 64 89 01 mov %eax,%fs:(%rcx)
> 15: 48 rex.W
> RSP: 002b:00007ffe2d0ad398 EFLAGS: 00000202 ORIG_RAX: 0000000000000031
> RAX: ffffffffffffffda RBX: 00007ffe2d0ad3d0 RCX: 00007f59b934a1e7
> RDX: 000000000000001c RSI: 00007ffe2d0ad3d0 RDI: 0000000000000005
> RBP: 0000000000000005 R08: 1999999999999999 R09: 0000000000000000
> R10: 00007f59b9253298 R11: 0000000000000202 R12: 00007ffe2d0ada61
> R13: 0000000000000000 R14: 0000562926516dd8 R15: 00007f59b9479000
> </TASK>
>
> Fixes: 6fe1e52490a9 ("sctp: check ipv6 addr with sk_bound_dev if set")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Xin Long <lucien.xin@...il.com>
> Cc: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Acked-by: Xin Long <lucien.xin@...il.com>
> ---
> net/sctp/ipv6.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index f7b809c0d142c0e6c8e29c2badc4428648117f31..38e2fbdcbeac4bf3185d98f8acae4aea531ca140 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -683,7 +683,7 @@ static int sctp_v6_available(union sctp_addr *addr, struct sctp_sock *sp)
> struct sock *sk = &sp->inet.sk;
> struct net *net = sock_net(sk);
> struct net_device *dev = NULL;
> - int type;
> + int type, res, bound_dev_if;
>
> type = ipv6_addr_type(in6);
> if (IPV6_ADDR_ANY == type)
> @@ -697,14 +697,21 @@ static int sctp_v6_available(union sctp_addr *addr, struct sctp_sock *sp)
> if (!(type & IPV6_ADDR_UNICAST))
> return 0;
>
> - if (sk->sk_bound_dev_if) {
> - dev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if);
> + rcu_read_lock();
> + bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
> + if (bound_dev_if) {
> + res = 0;
> + dev = dev_get_by_index_rcu(net, bound_dev_if);
> if (!dev)
> - return 0;
> + goto out;
> }
>
> - return ipv6_can_nonlocal_bind(net, &sp->inet) ||
> - ipv6_chk_addr(net, in6, dev, 0);
> + res = ipv6_can_nonlocal_bind(net, &sp->inet) ||
> + ipv6_chk_addr(net, in6, dev, 0);
> +
> +out:
> + rcu_read_unlock();
> + return res;
> }
>
> /* This function checks if the address is a valid address to be used for
> --
> 2.47.0.277.g8800431eea-goog
>
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