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Date: Thu, 29 Apr 2010 10:03:28 +0800
From: Hui Zhu <hui.zhu@...driver.com>
To: oss-security@...ts.openwall.com
CC: coley@...us.mitre.org, ZhangXiao <xiao.zhang@...driver.com>,
eugeneteo@...nel.sg
Subject: Re: CVE-2010-1173 kernel: skb_over_panic resulting
from multiple invalid parameter errors
Eugene Teo:
> https://bugzilla.redhat.com/CVE-2010-1173
> http://article.gmane.org/gmane.linux.network/159531
>
> Reported by Chris Guo from Nokia China via Red Hat Support. A similar
> issue was reported by Jukka Taimisto and Olli Jarva from Codenomicon Ltd
> via CERT-FI. This was also reported by Windriver on behalf of their
> customer via vendor-sec.
>
> Kernel crash occurs if sctp listening port receives malformatted init
> package.
>
> 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.
>
> This fix solves the problem by allowing our implementation to only
> report a fixed number of errors. When we encounter an error in
> parameter processing we allocate a chunk that is min(asoc->pathmtu,
> SCTP_DEFAULT_MAXSEGMENT), limiting our error reporting to a single mtu
> sized chunk. Parameter errors that grow beyond that value are discarded.
>
> Thanks, Eugene
>
Add Xiao to CC list.
Hui
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