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Date: Tue, 20 Jun 2023 09:15:39 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: David Ahern <dsahern@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org,
eric.dumazet@...il.com,
syzbot <syzkaller@...glegroups.com>,
Breno Leitao <leitao@...ian.org>,
Willem de Bruijn <willemb@...gle.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>
Subject: Re: [PATCH net-next] net: remove sk_is_ipmr() and sk_is_icmpv6()
helpers
David Ahern wrote:
> On 6/19/23 5:43 AM, Eric Dumazet wrote:
> > Blamed commit added these helpers for sake of detecting RAW
> > sockets specific ioctl.
> >
> > syzbot complained about it [1].
> >
> > Issue here is that RAW sockets could pretend there was no need
> > to call ipmr_sk_ioctl()
> >
> > Regardless of inet_sk(sk)->inet_num, we must be prepared
> > for ipmr_ioctl() being called later. This must happen
> > from ipmr_sk_ioctl() context only.
> >
> > We could add a safety check in ipmr_ioctl() at the risk of breaking
> > applications.
> >
> > Instead, remove sk_is_ipmr() and sk_is_icmpv6() because their
> > name would be misleading, once we change their implementation.
> >
> > [1]
> > BUG: KASAN: stack-out-of-bounds in ipmr_ioctl+0xb12/0xbd0 net/ipv4/ipmr.c:1654
> > Read of size 4 at addr ffffc90003aefae4 by task syz-executor105/5004
> >
> > CPU: 0 PID: 5004 Comm: syz-executor105 Not tainted 6.4.0-rc6-syzkaller-01304-gc08afcdcf952 #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> > Call Trace:
> > <TASK>
> > __dump_stack lib/dump_stack.c:88 [inline]
> > dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
> > print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
> > print_report mm/kasan/report.c:462 [inline]
> > kasan_report+0x11c/0x130 mm/kasan/report.c:572
> > ipmr_ioctl+0xb12/0xbd0 net/ipv4/ipmr.c:1654
> > raw_ioctl+0x4e/0x1e0 net/ipv4/raw.c:881
> > sock_ioctl_out net/core/sock.c:4186 [inline]
> > sk_ioctl+0x151/0x440 net/core/sock.c:4214
> > inet_ioctl+0x18c/0x380 net/ipv4/af_inet.c:1001
> > sock_do_ioctl+0xcc/0x230 net/socket.c:1189
> > sock_ioctl+0x1f8/0x680 net/socket.c:1306
> > vfs_ioctl fs/ioctl.c:51 [inline]
> > __do_sys_ioctl fs/ioctl.c:870 [inline]
> > __se_sys_ioctl fs/ioctl.c:856 [inline]
> > __x64_sys_ioctl+0x197/0x210 fs/ioctl.c:856
> > do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> > entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > RIP: 0033:0x7f2944bf6ad9
> > Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007ffd8897a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2944bf6ad9
> > RDX: 0000000000000000 RSI: 00000000000089e1 RDI: 0000000000000003
> > RBP: 00007f2944bbac80 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2944bbad10
> > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> > </TASK>
> >
> > The buggy address belongs to stack of task syz-executor105/5004
> > and is located at offset 36 in frame:
> > sk_ioctl+0x0/0x440 net/core/sock.c:4172
> >
> > This frame has 2 objects:
> > [32, 36) 'karg'
> > [48, 88) 'buffer'
> >
> > Fixes: e1d001fa5b47 ("net: ioctl: Use kernel memory on protocol ioctl callbacks")
> > Reported-by: syzbot <syzkaller@...glegroups.com>
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Cc: Breno Leitao <leitao@...ian.org>
> > Cc: Willem de Bruijn <willemb@...gle.com>
> > Cc: David Ahern <dsahern@...nel.org>
> > Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
> > ---
> > include/linux/icmpv6.h | 6 ------
> > include/linux/mroute.h | 11 -----------
> > net/core/sock.c | 4 ++--
> > 3 files changed, 2 insertions(+), 19 deletions(-)
> >
> > diff --git a/include/linux/icmpv6.h b/include/linux/icmpv6.h
> > index 1fe33e6741cca2685082da214afbc94c7974f4ce..db0f4fcfdaf4f138d75dc6c4073cb286364f2923 100644
> > --- a/include/linux/icmpv6.h
> > +++ b/include/linux/icmpv6.h
> > @@ -111,10 +111,4 @@ static inline bool icmpv6_is_err(int type)
> > return false;
> > }
> >
> > -static inline int sk_is_icmpv6(struct sock *sk)
> > -{
> > - return sk->sk_family == AF_INET6 &&
> > - inet_sk(sk)->inet_num == IPPROTO_ICMPV6;
> > -}
> > -
> > #endif
> > diff --git a/include/linux/mroute.h b/include/linux/mroute.h
> > index 94c6e6f549f0a503f6707d1175f1c47a0f0cd887..4c5003afee6c51962bc13879978845bc7daf08fa 100644
> > --- a/include/linux/mroute.h
> > +++ b/include/linux/mroute.h
> > @@ -16,12 +16,6 @@ static inline int ip_mroute_opt(int opt)
> > return opt >= MRT_BASE && opt <= MRT_MAX;
> > }
> >
> > -static inline int sk_is_ipmr(struct sock *sk)
> > -{
> > - return sk->sk_family == AF_INET &&
> > - inet_sk(sk)->inet_num == IPPROTO_IGMP;
> > -}
> > -
> > int ip_mroute_setsockopt(struct sock *, int, sockptr_t, unsigned int);
> > int ip_mroute_getsockopt(struct sock *, int, sockptr_t, sockptr_t);
> > int ipmr_ioctl(struct sock *sk, int cmd, void *arg);
> > @@ -57,11 +51,6 @@ static inline int ip_mroute_opt(int opt)
> > return 0;
> > }
> >
> > -static inline int sk_is_ipmr(struct sock *sk)
> > -{
> > - return 0;
> > -}
> > -
> > static inline bool ipmr_rule_default(const struct fib_rule *rule)
> > {
> > return true;
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index cff3e82514d17513bc96300dc18014083a0d7ea7..8ec8f4c9911f2a6dd3dd946798d512394d62a861 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -4199,9 +4199,9 @@ int sk_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)
> > {
> > int rc = 1;
> >
> > - if (sk_is_ipmr(sk))
> > + if (sk->sk_type == SOCK_RAW && sk->sk_family == AF_INET)
> > rc = ipmr_sk_ioctl(sk, cmd, arg);
> > - else if (sk_is_icmpv6(sk))
> > + else if (sk->sk_type == SOCK_RAW && sk->sk_family == AF_INET6)
> > rc = ip6mr_sk_ioctl(sk, cmd, arg);
> > else if (sk_is_phonet(sk))
> > rc = phonet_sk_ioctl(sk, cmd, arg);
>
> I was staring at the type when reviewing the original patch; I was
> expecting to see RAW based on where ipmr_ioctl (and v6 version) is
> called. That's why I asked about the testing of the patch, so I am not
> surprised by this followup.
>
> Reviewed-by: David Ahern <dsahern@...nel.org>
ipmr_ioctl is called from raw_ioctl without any additional checks on
inet_sk(sk)->inet_num too (as are ip6mr_ioctl and ipmr_compat_ioctl),
and casts to raw_sk(sk) without further checks. So this condition
lgtm too.
And conversely, interpreting inet_num(sk) as a protocol is only okay
after testing sk_type == SOCK_RAW.
Thanks for the fix, Eric
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
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