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mptcp: fix corrupt receiver key in MPC + data + checksum 

using packetdrill it's possible to observe that the receiver key contains
random values when clients transmit MP_CAPABLE with data and checksum (as
specified in RFC8684 §3.1). Fix the layout of mptcp_out_options, to avoid
using the skb extension copy when writing the MP_CAPABLE sub-option.

Fixes: d7b2690837 ("mptcp: shrink mptcp_out_options struct")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/233
Reported-by: Poorva Sonparote <psonparo@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Link: https://lore.kernel.org/r/20211027203855.264600-1-mathew.j.martineau@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Davide Caratti 2021-10-27 13:38:55 -07:00 committed by Jakub Kicinski
parent 27de809a3d
commit f7cc8890f3
2 changed files with 28 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/mptcp.h
View File

@ -69,6 +69,10 @@ struct mptcp_out_options {
struct {
u64 sndr_key;
u64 rcvr_key;
u64 data_seq;
u32 subflow_seq;
u16 data_len;
__sum16 csum;
};
struct {
struct mptcp_addr_info addr;

39
net/mptcp/options.c
View File

@ -485,11 +485,11 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
mpext = mptcp_get_ext(skb);
data_len = mpext ? mpext->data_len : 0;
/* we will check ext_copy.data_len in mptcp_write_options() to
/* we will check ops->data_len in mptcp_write_options() to
* discriminate between TCPOLEN_MPTCP_MPC_ACK_DATA and
* TCPOLEN_MPTCP_MPC_ACK
*/
opts->ext_copy.data_len = data_len;
opts->data_len = data_len;
opts->suboptions = OPTION_MPTCP_MPC_ACK;
opts->sndr_key = subflow->local_key;
opts->rcvr_key = subflow->remote_key;
@ -505,9 +505,9 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
len = TCPOLEN_MPTCP_MPC_ACK_DATA;
if (opts->csum_reqd) {
/* we need to propagate more info to csum the pseudo hdr */
opts->ext_copy.data_seq = mpext->data_seq;
opts->ext_copy.subflow_seq = mpext->subflow_seq;
opts->ext_copy.csum = mpext->csum;
opts->data_seq = mpext->data_seq;
opts->subflow_seq = mpext->subflow_seq;
opts->csum = mpext->csum;
len += TCPOLEN_MPTCP_DSS_CHECKSUM;
}
*size = ALIGN(len, 4);
@ -1227,7 +1227,7 @@ static void mptcp_set_rwin(const struct tcp_sock *tp)
WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
}
static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
static u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __sum16 sum)
{
struct csum_pseudo_header header;
__wsum csum;
@ -1237,15 +1237,21 @@ static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
* always the 64-bit value, irrespective of what length is used in the
* DSS option itself.
*/
header.data_seq = cpu_to_be64(mpext->data_seq);
header.subflow_seq = htonl(mpext->subflow_seq);
header.data_len = htons(mpext->data_len);
header.data_seq = cpu_to_be64(data_seq);
header.subflow_seq = htonl(subflow_seq);
header.data_len = htons(data_len);
header.csum = 0;
csum = csum_partial(&header, sizeof(header), ~csum_unfold(mpext->csum));
csum = csum_partial(&header, sizeof(header), ~csum_unfold(sum));
return (__force u16)csum_fold(csum);
}
static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
{
return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
mpext->csum);
}
void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
struct mptcp_out_options *opts)
{
@ -1337,7 +1343,7 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
len = TCPOLEN_MPTCP_MPC_SYN;
} else if (OPTION_MPTCP_MPC_SYNACK & opts->suboptions) {
len = TCPOLEN_MPTCP_MPC_SYNACK;
} else if (opts->ext_copy.data_len) {
} else if (opts->data_len) {
len = TCPOLEN_MPTCP_MPC_ACK_DATA;
if (opts->csum_reqd)
len += TCPOLEN_MPTCP_DSS_CHECKSUM;
@ -1366,14 +1372,17 @@ void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
put_unaligned_be64(opts->rcvr_key, ptr);
ptr += 2;
if (!opts->ext_copy.data_len)
if (!opts->data_len)
goto mp_capable_done;
if (opts->csum_reqd) {
put_unaligned_be32(opts->ext_copy.data_len << 16 |
mptcp_make_csum(&opts->ext_copy), ptr);
put_unaligned_be32(opts->data_len << 16 |
__mptcp_make_csum(opts->data_seq,
opts->subflow_seq,
opts->data_len,
opts->csum), ptr);
} else {
put_unaligned_be32(opts->ext_copy.data_len << 16 |
put_unaligned_be32(opts->data_len << 16 |
TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
}
ptr += 1;