From: Xin Long lucien.xin@gmail.com
[ Upstream commit ef16b1734f0a176277b7bb9c71a6d977a6ef3998 ]
sctp_sf_do_8_5_1_E_sa() is called when processing SHUTDOWN_ACK chunk in cookie_wait and cookie_echoed state.
The vtag in the chunk's sctphdr should be verified, otherwise, as later in chunk length check, it may send abort with the existent asoc's vtag, which can be exploited by one to cook a malicious chunk to terminate a SCTP asoc.
Note that when fails to verify the vtag from SHUTDOWN-ACK chunk, SHUTDOWN COMPLETE message will still be sent back to peer, but with the vtag from SHUTDOWN-ACK chunk, as said in 5) of rfc4960#section-8.4.
While at it, also remove the unnecessary chunk length check from sctp_sf_shut_8_4_5(), as it's already done in both places where it calls sctp_sf_shut_8_4_5().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sctp/sm_statefuns.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index a4874b55faab..2995d00bd5d0 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -3698,12 +3698,6 @@ static enum sctp_disposition sctp_sf_shut_8_4_5(
SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS);
- /* If the chunk length is invalid, we don't want to process - * the reset of the packet. - */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr))) - return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); - /* We need to discard the rest of the packet to prevent * potential bomming attacks from additional bundled chunks. * This is documented in SCTP Threats ID. @@ -3731,6 +3725,9 @@ enum sctp_disposition sctp_sf_do_8_5_1_E_sa(struct net *net, { struct sctp_chunk *chunk = arg;
+ if (!sctp_vtag_verify(chunk, asoc)) + asoc = NULL; + /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */ if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr))) return sctp_sf_violation_chunklen(net, ep, asoc, type, arg,