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From: Daniel Borkmann <dborkman@redhat.com>
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Date: Mon, 10 Nov 2014 17:54:26 +0100
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Subject: [PATCH] net: sctp: fix NULL pointer dereference in
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af->from_addr_param on malformed packet
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An SCTP server doing ASCONF will panic on malformed INIT ping-of-death
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in the form of:
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------------ INIT[PARAM: SET_PRIMARY_IP] ------------>
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While the INIT chunk parameter verification dissects through many things
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in order to detect malformed input, it misses to actually check parameters
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inside of parameters. E.g. RFC5061, section 4.2.4 proposes a 'set primary
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IP address' parameter in ASCONF, which has as a subparameter an address
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parameter.
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So an attacker may send a parameter type other than SCTP_PARAM_IPV4_ADDRESS
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or SCTP_PARAM_IPV6_ADDRESS, param_type2af() will subsequently return 0
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and thus sctp_get_af_specific() returns NULL, too, which we then happily
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dereference unconditionally through af->from_addr_param().
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The trace for the log:
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BUG: unable to handle kernel NULL pointer dereference at 0000000000000078
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IP: [<ffffffffa01e9c62>] sctp_process_init+0x492/0x990 [sctp]
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PGD 0
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Oops: 0000 [#1] SMP
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[...]
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Pid: 0, comm: swapper Not tainted 2.6.32-504.el6.x86_64 #1 Bochs Bochs
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RIP: 0010:[<ffffffffa01e9c62>] [<ffffffffa01e9c62>] sctp_process_init+0x492/0x990 [sctp]
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[...]
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Call Trace:
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<IRQ>
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[<ffffffffa01f2add>] ? sctp_bind_addr_copy+0x5d/0xe0 [sctp]
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[<ffffffffa01e1fcb>] sctp_sf_do_5_1B_init+0x21b/0x340 [sctp]
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[<ffffffffa01e3751>] sctp_do_sm+0x71/0x1210 [sctp]
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[<ffffffffa01e5c09>] ? sctp_endpoint_lookup_assoc+0xc9/0xf0 [sctp]
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[<ffffffffa01e61f6>] sctp_endpoint_bh_rcv+0x116/0x230 [sctp]
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[<ffffffffa01ee986>] sctp_inq_push+0x56/0x80 [sctp]
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[<ffffffffa01fcc42>] sctp_rcv+0x982/0xa10 [sctp]
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[<ffffffffa01d5123>] ? ipt_local_in_hook+0x23/0x28 [iptable_filter]
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[<ffffffff8148bdc9>] ? nf_iterate+0x69/0xb0
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[<ffffffff81496d10>] ? ip_local_deliver_finish+0x0/0x2d0
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[<ffffffff8148bf86>] ? nf_hook_slow+0x76/0x120
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[<ffffffff81496d10>] ? ip_local_deliver_finish+0x0/0x2d0
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[...]
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A minimal way to address this is to check for NULL as we do on all
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other such occasions where we know sctp_get_af_specific() could
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possibly return with NULL.
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Fixes: d6de3097592b ("[SCTP]: Add the handling of "Set Primary IP Address" parameter to INIT")
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Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
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Cc: Vlad Yasevich <vyasevich@gmail.com>
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Acked-by: Neil Horman <nhorman@tuxdriver.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/sctp/sm_make_chunk.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
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index ab734be8cb20..9f32741abb1c 100644
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--- a/net/sctp/sm_make_chunk.c
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+++ b/net/sctp/sm_make_chunk.c
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@@ -2609,6 +2609,9 @@ do_addr_param:
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addr_param = param.v + sizeof(sctp_addip_param_t);
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af = sctp_get_af_specific(param_type2af(param.p->type));
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+ if (af == NULL)
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+ break;
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+
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af->from_addr_param(&addr, addr_param,
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htons(asoc->peer.port), 0);
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--
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1.9.3
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