4.14-stable review patch. If anyone has any objections, please let me know.
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From: Lorenzo Bianconi lorenzo.bianconi@redhat.com
commit 62e7b6a57c7b9bf3c6fd99418eeec05b08a85c38 upstream.
Remove l2specific_len dependency while building l2tpv3 header or parsing the received frame since default L2-Specific Sublayer is always four bytes long and we don't need to rely on a user supplied value. Moreover in l2tp netlink code there are no sanity checks to enforce the relation between l2specific_len and l2specific_type, so sending a malformed netlink message is possible to set l2specific_type to L2TP_L2SPECTYPE_DEFAULT (or even L2TP_L2SPECTYPE_NONE) and set l2specific_len to a value greater than 4 leaking memory on the wire and sending corrupted frames.
Reviewed-by: Guillaume Nault g.nault@alphalink.fr Tested-by: Guillaume Nault g.nault@alphalink.fr Signed-off-by: Lorenzo Bianconi lorenzo.bianconi@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/l2tp/l2tp_core.c | 34 ++++++++++++++++------------------ net/l2tp/l2tp_core.h | 11 +++++++++++ 2 files changed, 27 insertions(+), 18 deletions(-)
--- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -758,11 +758,9 @@ void l2tp_recv_common(struct l2tp_sessio "%s: recv data ns=%u, session nr=%u\n", session->name, ns, session->nr); } + ptr += 4; }
- /* Advance past L2-specific header, if present */ - ptr += session->l2specific_len; - if (L2TP_SKB_CB(skb)->has_seq) { /* Received a packet with sequence numbers. If we're the LNS, * check if we sre sending sequence numbers and if not, @@ -1084,21 +1082,20 @@ static int l2tp_build_l2tpv3_header(stru memcpy(bufp, &session->cookie[0], session->cookie_len); bufp += session->cookie_len; } - if (session->l2specific_len) { - if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { - u32 l2h = 0; - if (session->send_seq) { - l2h = 0x40000000 | session->ns; - session->ns++; - session->ns &= 0xffffff; - l2tp_dbg(session, L2TP_MSG_SEQ, - "%s: updated ns to %u\n", - session->name, session->ns); - } + if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) { + u32 l2h = 0;
- *((__be32 *) bufp) = htonl(l2h); + if (session->send_seq) { + l2h = 0x40000000 | session->ns; + session->ns++; + session->ns &= 0xffffff; + l2tp_dbg(session, L2TP_MSG_SEQ, + "%s: updated ns to %u\n", + session->name, session->ns); } - bufp += session->l2specific_len; + + *((__be32 *)bufp) = htonl(l2h); + bufp += 4; }
return bufp - optr; @@ -1764,7 +1761,7 @@ int l2tp_session_delete(struct l2tp_sess EXPORT_SYMBOL_GPL(l2tp_session_delete);
/* We come here whenever a session's send_seq, cookie_len or - * l2specific_len parameters are set. + * l2specific_type parameters are set. */ void l2tp_session_set_header_len(struct l2tp_session *session, int version) { @@ -1773,7 +1770,8 @@ void l2tp_session_set_header_len(struct if (session->send_seq) session->hdr_len += 4; } else { - session->hdr_len = 4 + session->cookie_len + session->l2specific_len; + session->hdr_len = 4 + session->cookie_len; + session->hdr_len += l2tp_get_l2specific_len(session); if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP) session->hdr_len += 4; } --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -320,6 +320,17 @@ do { \ #define l2tp_session_dec_refcount(s) l2tp_session_dec_refcount_1(s) #endif
+static inline int l2tp_get_l2specific_len(struct l2tp_session *session) +{ + switch (session->l2specific_type) { + case L2TP_L2SPECTYPE_DEFAULT: + return 4; + case L2TP_L2SPECTYPE_NONE: + default: + return 0; + } +} + #define l2tp_printk(ptr, type, func, fmt, ...) \ do { \ if (((ptr)->debug) & (type)) \