| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Fri, 6 Jun 2014 10:44:02 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: Alexey Preobrazhensky <preobr@...gle.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Kostya Serebryany <kcc@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Lars Bull <larsbull@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Bruce Curtis <brutus@...gle.com>,
Maciej Żenczykowski <maze@...gle.com>,
dormando <dormando@...ia.net>
Subject: Re: Potential race in ip4_datagram_release_cb
On Fri, Jun 6, 2014 at 9:16 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Fri, 2014-06-06 at 08:59 -0700, Alexei Starovoitov wrote:
>> On Fri, Jun 6, 2014 at 5:56 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> > On Fri, 2014-06-06 at 15:29 +0400, Alexey Preobrazhensky wrote:
>> >> Hello,
>> >>
>> >> I’m working on AddressSanitizer[1] -- a tool that detects
>> >> use-after-free and out-of-bounds bugs in kernel.
>> >>
>> >> We’ve encountered a heap-use-after-free in ip4_datagram_release_cb()
>> >> in linux kernel 3.15-rc5 (revision
>> >> 60b5f90d0fac7585f1a43ccdad06787b97eda0ab).
>> >>
>> >> It seems to be a race between dst_release() and
>> >> ip4_datagram_release_cb() on an object from ip_dst_cache slab, all
>> >> during the ip4_datagram_connect() call.
>> >>
>> >> This heap-use-after-free was triggered under trinity syscall fuzzer,
>> >> so there is no reproducer.
>> >>
>> >> It would be great if someone familiar with the code took time to look
>> >> into this report.
>> >>
>> >> Thanks,
>> >> Alexey
>> >>
>> >> [1] https://code.google.com/p/address-sanitizer/wiki/AddressSanitizerForKernel
>> >>
>> >>
>> >> AddressSanitizer: heap-use-after-free in ipv4_dst_check
>> >> Read of size 2 by thread T15453:
>> >> [<ffffffff817daa3a>] ipv4_dst_check+0x1a/0x90 ./net/ipv4/route.c:1116
>> >> [<ffffffff8175b789>] __sk_dst_check+0x89/0xe0 ./net/core/sock.c:531
>> >> [<ffffffff81830a36>] ip4_datagram_release_cb+0x46/0x390 ??:0
>> >> [<ffffffff8175eaea>] release_sock+0x17a/0x230 ./net/core/sock.c:2413
>> >> [<ffffffff81830882>] ip4_datagram_connect+0x462/0x5d0 ??:0
>> >> [<ffffffff81846d06>] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet.c:534
>> >> [<ffffffff817580ac>] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701
>> >> [<ffffffff817596ce>] SyS_connect+0xe/0x10 ./net/socket.c:1682
>> >> [<ffffffff818b0a29>] system_call_fastpath+0x16/0x1b
>> >> ./arch/x86/kernel/entry_64.S:629
>> >>
>> >> Freed by thread T15455:
>> >> [<ffffffff8178d9b8>] dst_destroy+0xa8/0x160 ./net/core/dst.c:251
>> >> [<ffffffff8178de25>] dst_release+0x45/0x80 ./net/core/dst.c:280
>> >> [<ffffffff818304c1>] ip4_datagram_connect+0xa1/0x5d0 ??:0
>> >> [<ffffffff81846d06>] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet.c:534
>> >> [<ffffffff817580ac>] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701
>> >> [<ffffffff817596ce>] SyS_connect+0xe/0x10 ./net/socket.c:1682
>> >> [<ffffffff818b0a29>] system_call_fastpath+0x16/0x1b
>> >> ./arch/x86/kernel/entry_64.S:629
>> >>
>> >> Allocated by thread T15453:
>> >> [<ffffffff8178d291>] dst_alloc+0x81/0x2b0 ./net/core/dst.c:171
>> >> [<ffffffff817db3b7>] rt_dst_alloc+0x47/0x50 ./net/ipv4/route.c:1406
>> >> [< inlined >] __ip_route_output_key+0x3e8/0xf70
>> >> __mkroute_output ./net/ipv4/route.c:1939
>> >> [<ffffffff817dde08>] __ip_route_output_key+0x3e8/0xf70 ./net/ipv4/route.c:2161
>> >> [<ffffffff817deb34>] ip_route_output_flow+0x14/0x30 ./net/ipv4/route.c:2249
>> >> [<ffffffff81830737>] ip4_datagram_connect+0x317/0x5d0 ??:0
>> >> [<ffffffff81846d06>] inet_dgram_connect+0x76/0xd0 ./net/ipv4/af_inet.c:534
>> >> [<ffffffff817580ac>] SYSC_connect+0x15c/0x1c0 ./net/socket.c:1701
>> >> [<ffffffff817596ce>] SyS_connect+0xe/0x10 ./net/socket.c:1682
>> >> [<ffffffff818b0a29>] system_call_fastpath+0x16/0x1b
>> >> ./arch/x86/kernel/entry_64.S:629
>> >>
>> >> The buggy address ffff880024ff2266 is located 102 bytes inside
>> >> of 192-byte region [ffff880024ff2200, ffff880024ff22c0)
>> >>
>> >> Memory state around the buggy address:
>> >> ffff880024ff1d00: ffffffff fffrrrrr rrrrrrrr rrrrrrrr
>> >> ffff880024ff1e00: ffffffff ffffffff ffffffff fffrrrrr
>> >> ffff880024ff1f00: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
>> >> ffff880024ff2000: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
>> >> ffff880024ff2100: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
>> >> >ffff880024ff2200: ffffffff ffffffff ffffffff rrrrrrrr
>> >> ^
>> >> ffff880024ff2300: rrrrrrrr rrrrrrrr ........ ........
>> >> ffff880024ff2400: ........ rrrrrrrr rrrrrrrr rrrrrrrr
>> >> ffff880024ff2500: ffffffff ffffffff ffffffff rrrrrrrr
>> >> ffff880024ff2600: rrrrrrrr rrrrrrrr ffffffff ffffffff
>> >> ffff880024ff2700: ffffffff rrrrrrrr rrrrrrrr rrrrrrrr
>> >> Legend:
>> >> f - 8 freed bytes
>> >> r - 8 redzone bytes
>> >> . - 8 allocated bytes
>> >> x=1..7 - x allocated bytes + (8-x) redzone bytes
>> >> --
>> >
>> >
>> > Yeah, we had many reports in the past that something was wrong ...
>> >
>> > Your nice report made me take a look, finally :(
>> >
>> > Problem comes from
>> >
>> > net/ipv4/udp.c:1008: sk_dst_set(sk, dst_clone(&rt->dst));
>> >
>> > Could you try following patch ?
>> >
>> > Thanks !
>> >
>> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
>> > index 4468e1adc094..d5e68ee63b8f 100644
>> > --- a/net/ipv4/udp.c
>> > +++ b/net/ipv4/udp.c
>> > @@ -1004,8 +1004,11 @@ int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
>> > if ((rt->rt_flags & RTCF_BROADCAST) &&
>> > !sock_flag(sk, SOCK_BROADCAST))
>> > goto out;
>> > - if (connected)
>> > - sk_dst_set(sk, dst_clone(&rt->dst));
>> > + if (connected) {
>> > + spin_lock_bh(&sk->sk_lock.slock);
>> > + __sk_dst_set(sk, dst_clone(&rt->dst));
>> > + spin_unlock_bh(&sk->sk_lock.slock);
>> > + }
>>
>> Nice catch.
>> Should then we change sk_dst_set() itself to do spin_lock_bh unconditionally?
>> Seems overhead is smaller, than checking all possible callsites manually.
>>
>> cc-ing Dormando as well.
>
>
> Real problem is that sk_dst_set() uses a different lock. I never
> understood how this was supposed to work.
we probably need to test the assumption in the sk_dst_set() comment:
/* This can be called while sk is owned by the caller only */
I don't understand why this piece of code doesn't do:
old_dst = rcu_dereference_check(sk->sk_dst_cache,
sock_owned_by_user(sk) || lockdep_is_held(&sk->sk_lock.slock));
like sk_dst_get does...
If I'm reading the code correctly, at the time of sk_dst_set() call
from udp_sendmsg()
the sk_lock.slock is not held and sock_owned_by_user(sk) is false as well.
Same not held condition is in the first sk_dst_reset() call from
ip4_datagram_connect().
Though the lock is properly held from release_sock()->ip4_datagram_release_cb()
Cannot agree more with Eric "how is it supposed to work?"
> We should either :
>
> 1) use xchg() and no lock at all to change sk_dst_cache, as we did for
> sk_rx_dst ( cf udp_sk_rx_dst_set() )
>
> 2) No longer use sk_dst_lock, and always use the socket lock
> (sk->sk_lock.slock) instead.
Probably needs some combination of both.
sk_dst_lock seems useless for ipv4.
What the following suppose to do in ipv6_update_options() ?!
spin_lock(&sk->sk_dst_lock);
opt = xchg(&inet6_sk(sk)->opt, opt);
spin_unlock(&sk->sk_dst_lock);
seems ipv6 is reusing the same lock for completely different reason.
>
>
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists