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Date: Thu, 13 Jul 2017 20:14:15 +0200
From: Alexander Potapenko <glider@...gle.com>
To: Dmitriy Vyukov <dvyukov@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
David Miller <davem@...emloft.net>,
lucien xin <lucien.xin@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH] sctp: don't dereference ptr before leaving _sctp_walk_{params,errors}()
On Thu, Jul 13, 2017 at 8:10 PM, Alexander Potapenko <glider@...gle.com> wrote:
> If the iterator (|pos.p| or |err|) has already reached the end of
> chunk, we shouldn't access iterator->length.
>
> This bug has been detected by KMSAN. For the following pair of system
> calls:
>
> socket(PF_INET6, SOCK_STREAM, 0x84 /* IPPROTO_??? */) = 3
> sendto(3, "A", 1, MSG_OOB, {sa_family=AF_INET6, sin6_port=htons(0),
> inet_pton(AF_INET6, "::1", &sin6_addr), sin6_flowinfo=0,
> sin6_scope_id=0}, 28) = 1
>
> the tool has reported a use of uninitialized memory:
>
> ==================================================================
> BUG: KMSAN: use of uninitialized memory in sctp_rcv+0x17b8/0x43b0
> CPU: 1 PID: 2940 Comm: probe Not tainted 4.11.0-rc5+ #2926
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
> 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:16
> dump_stack+0x172/0x1c0 lib/dump_stack.c:52
> kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:927
> __msan_warning_32+0x61/0xb0 mm/kmsan/kmsan_instr.c:469
> __sctp_rcv_init_lookup net/sctp/input.c:1074
> __sctp_rcv_lookup_harder net/sctp/input.c:1233
> __sctp_rcv_lookup net/sctp/input.c:1255
> sctp_rcv+0x17b8/0x43b0 net/sctp/input.c:170
> sctp6_rcv+0x32/0x70 net/sctp/ipv6.c:984
> ip6_input_finish+0x82f/0x1ee0 net/ipv6/ip6_input.c:279
> NF_HOOK ./include/linux/netfilter.h:257
> ip6_input+0x239/0x290 net/ipv6/ip6_input.c:322
> dst_input ./include/net/dst.h:492
> ip6_rcv_finish net/ipv6/ip6_input.c:69
> NF_HOOK ./include/linux/netfilter.h:257
> ipv6_rcv+0x1dbd/0x22e0 net/ipv6/ip6_input.c:203
> __netif_receive_skb_core+0x2f6f/0x3a20 net/core/dev.c:4208
> __netif_receive_skb net/core/dev.c:4246
> process_backlog+0x667/0xba0 net/core/dev.c:4866
> napi_poll net/core/dev.c:5268
> net_rx_action+0xc95/0x1590 net/core/dev.c:5333
> __do_softirq+0x485/0x942 kernel/softirq.c:284
> do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902
> </IRQ>
> do_softirq kernel/softirq.c:328
> __local_bh_enable_ip+0x25b/0x290 kernel/softirq.c:181
> local_bh_enable+0x37/0x40 ./include/linux/bottom_half.h:31
> rcu_read_unlock_bh ./include/linux/rcupdate.h:931
> ip6_finish_output2+0x19b2/0x1cf0 net/ipv6/ip6_output.c:124
> ip6_finish_output+0x764/0x970 net/ipv6/ip6_output.c:149
> NF_HOOK_COND ./include/linux/netfilter.h:246
> ip6_output+0x456/0x520 net/ipv6/ip6_output.c:163
> dst_output ./include/net/dst.h:486
> NF_HOOK ./include/linux/netfilter.h:257
> ip6_xmit+0x1841/0x1c00 net/ipv6/ip6_output.c:261
> sctp_v6_xmit+0x3b7/0x470 net/sctp/ipv6.c:225
> sctp_packet_transmit+0x38cb/0x3a20 net/sctp/output.c:632
> sctp_outq_flush+0xeb3/0x46e0 net/sctp/outqueue.c:885
> sctp_outq_uncork+0xb2/0xd0 net/sctp/outqueue.c:750
> sctp_side_effects net/sctp/sm_sideeffect.c:1773
> sctp_do_sm+0x6962/0x6ec0 net/sctp/sm_sideeffect.c:1147
> sctp_primitive_ASSOCIATE+0x12c/0x160 net/sctp/primitive.c:88
> sctp_sendmsg+0x43e5/0x4f90 net/sctp/socket.c:1954
> inet_sendmsg+0x498/0x670 net/ipv4/af_inet.c:762
> sock_sendmsg_nosec net/socket.c:633
> sock_sendmsg net/socket.c:643
> SYSC_sendto+0x608/0x710 net/socket.c:1696
> SyS_sendto+0x8a/0xb0 net/socket.c:1664
> do_syscall_64+0xe6/0x130 arch/x86/entry/common.c:285
> entry_SYSCALL64_slow_path+0x25/0x25 arch/x86/entry/entry_64.S:246
> RIP: 0033:0x401133
> RSP: 002b:00007fff6d99cd38 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 00000000004002b0 RCX: 0000000000401133
> RDX: 0000000000000001 RSI: 0000000000494088 RDI: 0000000000000003
> RBP: 00007fff6d99cd90 R08: 00007fff6d99cd50 R09: 000000000000001c
> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
> R13: 00000000004063d0 R14: 0000000000406460 R15: 0000000000000000
> origin:
> save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302
> kmsan_internal_poison_shadow+0xb1/0x1a0 mm/kmsan/kmsan.c:198
> kmsan_poison_shadow+0x6d/0xc0 mm/kmsan/kmsan.c:211
> slab_alloc_node mm/slub.c:2743
> __kmalloc_node_track_caller+0x200/0x360 mm/slub.c:4351
> __kmalloc_reserve net/core/skbuff.c:138
> __alloc_skb+0x26b/0x840 net/core/skbuff.c:231
> alloc_skb ./include/linux/skbuff.h:933
> sctp_packet_transmit+0x31e/0x3a20 net/sctp/output.c:570
> sctp_outq_flush+0xeb3/0x46e0 net/sctp/outqueue.c:885
> sctp_outq_uncork+0xb2/0xd0 net/sctp/outqueue.c:750
> sctp_side_effects net/sctp/sm_sideeffect.c:1773
> sctp_do_sm+0x6962/0x6ec0 net/sctp/sm_sideeffect.c:1147
> sctp_primitive_ASSOCIATE+0x12c/0x160 net/sctp/primitive.c:88
> sctp_sendmsg+0x43e5/0x4f90 net/sctp/socket.c:1954
> inet_sendmsg+0x498/0x670 net/ipv4/af_inet.c:762
> sock_sendmsg_nosec net/socket.c:633
> sock_sendmsg net/socket.c:643
> SYSC_sendto+0x608/0x710 net/socket.c:1696
> SyS_sendto+0x8a/0xb0 net/socket.c:1664
> do_syscall_64+0xe6/0x130 arch/x86/entry/common.c:285
> return_from_SYSCALL_64+0x0/0x6a arch/x86/entry/entry_64.S:246
> ==================================================================
>
> Signed-off-by: Alexander Potapenko <glider@...gle.com>
> ---
> include/net/sctp/sctp.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index a9519a06a23b..f13632ee33f0 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -469,6 +469,7 @@ _sctp_walk_params((pos), (chunk), ntohs((chunk)->chunk_hdr.length), member)
>
> #define _sctp_walk_params(pos, chunk, end, member)\
> for (pos.v = chunk->member;\
> + pos.v < (void *)chunk + end &&\
checkpatch.pl warns about spaces here, but I wanted to be consistent
with the rest of the file.
> pos.v <= (void *)chunk + end - ntohs(pos.p->length) &&\
> ntohs(pos.p->length) >= sizeof(struct sctp_paramhdr);\
> pos.v += SCTP_PAD4(ntohs(pos.p->length)))
> @@ -479,6 +480,7 @@ _sctp_walk_errors((err), (chunk_hdr), ntohs((chunk_hdr)->length))
> #define _sctp_walk_errors(err, chunk_hdr, end)\
> for (err = (sctp_errhdr_t *)((void *)chunk_hdr + \
> sizeof(struct sctp_chunkhdr));\
> + (void *)err <= (void *)chunk_hdr + end &&\
> (void *)err <= (void *)chunk_hdr + end - ntohs(err->length) &&\
> ntohs(err->length) >= sizeof(sctp_errhdr_t); \
> err = (sctp_errhdr_t *)((void *)err + SCTP_PAD4(ntohs(err->length))))
> --
> 2.13.2.932.g7449e964c-goog
>
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
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