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Message-ID: <20100428142147.GB4818@hmsreliant.think-freely.org>
Date: Wed, 28 Apr 2010 10:21:47 -0400
From: Neil Horman <nhorman@...driver.com>
To: Vlad Yasevich <vladislav.yasevich@...com>
Cc: sri@...ibm.com, linux-sctp@...r.kernel.org, eteo@...hat.com,
netdev@...r.kernel.org, davem@...emloft.net, security@...nel.org
Subject: Re: [PATCH]: sctp: Fix skb_over_panic resulting from multiple
invalid parameter errors (CVE-2010-1173)
On Wed, Apr 28, 2010 at 10:00:37AM -0400, Vlad Yasevich wrote:
> I have this patch and a few others already queued.
>
> I was planning on sending these today for stable.
>
> Here is the full list of stable patches I have:
>
> sctp: Fix oops when sending queued ASCONF chunks
> sctp: fix to calc the INIT/INIT-ACK chunk length correctly is set
> sctp: per_cpu variables should be in bh_disabled section
> sctp: fix potential reference of a freed pointer
> sctp: avoid irq lock inversion while call sk->sk_data_ready()
>
> -vlad
>
Are you sure? this oops looks _very_ simmilar to the INIT/INIT-ACK length
calculation oops described above, but is in fact different, and requires this
patch, from what I can see. The right fix might be in the ASCONF chunk patch
you list above, but I don't see that in your tree at the moment, so I can't be
sure.
Neil
> Neil Horman wrote:
> > Hey-
> > Recently, it was reported to me that the kernel could oops in the
> > following way:
> >
> > <5> kernel BUG at net/core/skbuff.c:91!
> > <5> invalid operand: 0000 [#1]
> > <5> Modules linked in: sctp netconsole nls_utf8 autofs4 sunrpc iptable_filter
> > ip_tables cpufreq_powersave parport_pc lp parport vmblock(U) vsock(U) vmci(U)
> > vmxnet(U) vmmemctl(U) vmhgfs(U) acpiphp dm_mirror dm_mod button battery ac md5
> > ipv6 uhci_hcd ehci_hcd snd_ens1371 snd_rawmidi snd_seq_device snd_pcm_oss
> > snd_mixer_oss snd_pcm snd_timer snd_page_alloc snd_ac97_codec snd soundcore
> > pcnet32 mii floppy ext3 jbd ata_piix libata mptscsih mptsas mptspi mptscsi
> > mptbase sd_mod scsi_mod
> > <5> CPU: 0
> > <5> EIP: 0060:[<c02bff27>] Not tainted VLI
> > <5> EFLAGS: 00010216 (2.6.9-89.0.25.EL)
> > <5> EIP is at skb_over_panic+0x1f/0x2d
> > <5> eax: 0000002c ebx: c033f461 ecx: c0357d96 edx: c040fd44
> > <5> esi: c033f461 edi: df653280 ebp: 00000000 esp: c040fd40
> > <5> ds: 007b es: 007b ss: 0068
> > <5> Process swapper (pid: 0, threadinfo=c040f000 task=c0370be0)
> > <5> Stack: c0357d96 e0c29478 00000084 00000004 c033f461 df653280 d7883180
> > e0c2947d
> > <5> 00000000 00000080 df653490 00000004 de4f1ac0 de4f1ac0 00000004
> > df653490
> > <5> 00000001 e0c2877a 08000800 de4f1ac0 df653490 00000000 e0c29d2e
> > 00000004
> > <5> Call Trace:
> > <5> [<e0c29478>] sctp_addto_chunk+0xb0/0x128 [sctp]
> > <5> [<e0c2947d>] sctp_addto_chunk+0xb5/0x128 [sctp]
> > <5> [<e0c2877a>] sctp_init_cause+0x3f/0x47 [sctp]
> > <5> [<e0c29d2e>] sctp_process_unk_param+0xac/0xb8 [sctp]
> > <5> [<e0c29e90>] sctp_verify_init+0xcc/0x134 [sctp]
> > <5> [<e0c20322>] sctp_sf_do_5_1B_init+0x83/0x28e [sctp]
> > <5> [<e0c25333>] sctp_do_sm+0x41/0x77 [sctp]
> > <5> [<c01555a4>] cache_grow+0x140/0x233
> > <5> [<e0c26ba1>] sctp_endpoint_bh_rcv+0xc5/0x108 [sctp]
> > <5> [<e0c2b863>] sctp_inq_push+0xe/0x10 [sctp]
> > <5> [<e0c34600>] sctp_rcv+0x454/0x509 [sctp]
> > <5> [<e084e017>] ipt_hook+0x17/0x1c [iptable_filter]
> > <5> [<c02d005e>] nf_iterate+0x40/0x81
> > <5> [<c02e0bb9>] ip_local_deliver_finish+0x0/0x151
> > <5> [<c02e0c7f>] ip_local_deliver_finish+0xc6/0x151
> > <5> [<c02d0362>] nf_hook_slow+0x83/0xb5
> > <5> [<c02e0bb2>] ip_local_deliver+0x1a2/0x1a9
> > <5> [<c02e0bb9>] ip_local_deliver_finish+0x0/0x151
> > <5> [<c02e103e>] ip_rcv+0x334/0x3b4
> > <5> [<c02c66fd>] netif_receive_skb+0x320/0x35b
> > <5> [<e0a0928b>] init_stall_timer+0x67/0x6a [uhci_hcd]
> > <5> [<c02c67a4>] process_backlog+0x6c/0xd9
> > <5> [<c02c690f>] net_rx_action+0xfe/0x1f8
> > <5> [<c012a7b1>] __do_softirq+0x35/0x79
> > <5> [<c0107efb>] handle_IRQ_event+0x0/0x4f
> > <5> [<c01094de>] do_softirq+0x46/0x4d
> >
> > Its an skb_over_panic BUG halt that results from processing an init chunk in
> > which too many of its variable length parameters are in some way malformed.
> >
> > The problem is in sctp_process_unk_param:
> > if (NULL == *errp)
> > *errp = sctp_make_op_error_space(asoc, chunk,
> > ntohs(chunk->chunk_hdr->length));
> >
> > if (*errp) {
> > sctp_init_cause(*errp, SCTP_ERROR_UNKNOWN_PARAM,
> > WORD_ROUND(ntohs(param.p->length)));
> > sctp_addto_chunk(*errp,
> > WORD_ROUND(ntohs(param.p->length)),
> > param.v);
> >
> > When we allocate an error chunk, we assume that the worst case scenario requires
> > that we have chunk_hdr->length data allocated, which would be correct nominally,
> > given that we call sctp_addto_chunk for the violating parameter. Unfortunately,
> > we also, in sctp_init_cause insert a sctp_errhdr_t structure into the error
> > chunk, so the worst case situation in which all parameters are in violation
> > requires chunk_hdr->length+(sizeof(sctp_errhdr_t)*param_count) bytes of data.
> >
> > The result of this error is that a deliberately malformed packet sent to a
> > listening host can cause a remote DOS, described in CVE-2010-1173:
> > http://cve.mitre.org/cgi-bin/cvename.cgi?name=2010-1173
> >
> > I've tested the below fix and confirmed that it fixes the issue. It
> > pre-allocates the error chunk in sctp_verify_init, where we are able to count
> > the total number of variable length parameters, so we know how many error
> > headers we might need. Then we simply use that chunk, if we find an error, or
> > discard/free it if all the parameters are valid. Applies on top of the
> > lksctp-dev tree
> >
> > Signed-off-by: Neil Horman <nhorman@...driver.com>
> >
> >
> > sm_make_chunk.c | 24 ++++++++++++++++++++++--
> > 1 file changed, 22 insertions(+), 2 deletions(-)
> >
> >
> > diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> > index f592163..990457b 100644
> > --- a/net/sctp/sm_make_chunk.c
> > +++ b/net/sctp/sm_make_chunk.c
> > @@ -2134,6 +2134,8 @@ int sctp_verify_init(const struct sctp_association *asoc,
> > union sctp_params param;
> > int has_cookie = 0;
> > int result;
> > + unsigned int param_cnt;
> > + unsigned int len;
> >
> > /* Verify stream values are non-zero. */
> > if ((0 == peer_init->init_hdr.num_outbound_streams) ||
> > @@ -2149,6 +2151,7 @@ int sctp_verify_init(const struct sctp_association *asoc,
> >
> > if (SCTP_PARAM_STATE_COOKIE == param.p->type)
> > has_cookie = 1;
> > + param_cnt++;
> >
> > } /* for (loop through all parameters) */
> >
> > @@ -2169,6 +2172,20 @@ int sctp_verify_init(const struct sctp_association *asoc,
> > return sctp_process_missing_param(asoc, SCTP_PARAM_STATE_COOKIE,
> > chunk, errp);
> >
> > + if (!*errp) {
> > + /*
> > + * Pre-allocate the error packet here
> > + * we do this as we need to reserve space
> > + * for the worst case scenario in which
> > + * every parameter is in error and needs
> > + * an errhdr attached to it
> > + */
> > + len = ntohs(chunk->chunk_hdr->length);
> > + len += sizeof(sctp_errhdr_t)*param_cnt;
> > +
> > + *errp = sctp_make_op_error_space(asoc, chunk, len);
> > + }
> > +
> > /* Verify all the variable length parameters */
> > sctp_walk_params(param, peer_init, init_hdr.params) {
> >
> > @@ -2176,9 +2193,11 @@ int sctp_verify_init(const struct sctp_association *asoc,
> > switch (result) {
> > case SCTP_IERROR_ABORT:
> > case SCTP_IERROR_NOMEM:
> > - return 0;
> > case SCTP_IERROR_ERROR:
> > - return 1;
> > + len = ntohs((*errp)->chunk_hdr->length);
> > + if ((*errp) && (len == sizeof(sctp_chunkhdr_t)))
> > + sctp_chunk_free(*errp);
> > + return (result == SCTP_IERROR_ERROR) ? 1 : 0;
> > case SCTP_IERROR_NO_ERROR:
> > default:
> > break;
> > @@ -2186,6 +2205,7 @@ int sctp_verify_init(const struct sctp_association *asoc,
> >
> > } /* for (loop through all parameters) */
> >
> > + sctp_chunk_free(*errp);
> > return 1;
> > }
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
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