From ba43cdd87d0aaed69ef1bb14a91c3e767a4c210f Mon Sep 17 00:00:00 2001 From: Marcelo Ricardo Leitner Date: Tue, 25 Oct 2016 14:27:39 -0200 Subject: [PATCH] sctp: validate chunk len before actually using it commit bf911e985d6bbaa328c20c3e05f4eb03de11fdd6 upstream. Andrey Konovalov reported that KASAN detected that SCTP was using a slab beyond the boundaries. It was caused because when handling out of the blue packets in function sctp_sf_ootb() it was checking the chunk len only after already processing the first chunk, validating only for the 2nd and subsequent ones. The fix is to just move the check upwards so it's also validated for the 1st chunk. Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Signed-off-by: Marcelo Ricardo Leitner Reviewed-by: Xin Long Acked-by: Neil Horman Signed-off-by: David S. Miller [bwh: Backported to 3.2: moved code is slightly different] Signed-off-by: Ben Hutchings --- net/sctp/sm_statefuns.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index 4e0a9b934233..6b22d6a2dd63 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -3354,6 +3354,12 @@ sctp_disposition_t sctp_sf_ootb(const struct sctp_endpoint *ep, return sctp_sf_violation_chunklen(ep, asoc, type, arg, commands); + /* Report violation if chunk len overflows */ + ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length)); + if (ch_end > skb_tail_pointer(skb)) + return sctp_sf_violation_chunklen(ep, asoc, type, arg, + commands); + /* Now that we know we at least have a chunk header, * do things that are type appropriate. */ @@ -3385,12 +3391,6 @@ sctp_disposition_t sctp_sf_ootb(const struct sctp_endpoint *ep, } } - /* Report violation if chunk len overflows */ - ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length)); - if (ch_end > skb_tail_pointer(skb)) - return sctp_sf_violation_chunklen(ep, asoc, type, arg, - commands); - ch = (sctp_chunkhdr_t *) ch_end; } while (ch_end < skb_tail_pointer(skb)); -- 2.30.2