From: Dan Carpenter dan.carpenter@oracle.com
[ Upstream commit 66d42ed8b25b64eb63111a2b8582c5afc8bf1105 ]
There are a couple bugs here: 1) If opt[1] is zero then this results in a forever loop. If the value is less than 2 then it is invalid. 2) It assumes that "len" is more than sizeof(valid_accm) or 6 which can result in memory corruption.
In the case of LCP_OPTION_ACCM, then we should check "opt[1]" instead of "len" because, if "opt[1]" is less than sizeof(valid_accm) then "nak_len" gets out of sync and it can lead to memory corruption in the next iterations through the loop. In case of LCP_OPTION_MAGIC, the only valid value for opt[1] is 6, but the code is trying to log invalid data so we should only discard the data when "len" is less than 6 because that leads to a read overflow.
Reported-by: ChenNan Of Chaitin Security Research Lab whutchennan@gmail.com Fixes: e022c2f07ae5 ("WAN: new synchronous PPP implementation for generic HDLC.") Signed-off-by: Dan Carpenter dan.carpenter@oracle.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/wan/hdlc_ppp.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/net/wan/hdlc_ppp.c +++ b/drivers/net/wan/hdlc_ppp.c @@ -383,11 +383,8 @@ static void ppp_cp_parse_cr(struct net_d }
for (opt = data; len; len -= opt[1], opt += opt[1]) { - if (len < 2 || len < opt[1]) { - dev->stats.rx_errors++; - kfree(out); - return; /* bad packet, drop silently */ - } + if (len < 2 || opt[1] < 2 || len < opt[1]) + goto err_out;
if (pid == PID_LCP) switch (opt[0]) { @@ -395,6 +392,8 @@ static void ppp_cp_parse_cr(struct net_d continue; /* MRU always OK and > 1500 bytes? */
case LCP_OPTION_ACCM: /* async control character map */ + if (opt[1] < sizeof(valid_accm)) + goto err_out; if (!memcmp(opt, valid_accm, sizeof(valid_accm))) continue; @@ -406,6 +405,8 @@ static void ppp_cp_parse_cr(struct net_d } break; case LCP_OPTION_MAGIC: + if (len < 6) + goto err_out; if (opt[1] != 6 || (!opt[2] && !opt[3] && !opt[4] && !opt[5])) break; /* reject invalid magic number */ @@ -424,6 +425,11 @@ static void ppp_cp_parse_cr(struct net_d ppp_cp_event(dev, pid, RCR_GOOD, CP_CONF_ACK, id, req_len, data);
kfree(out); + return; + +err_out: + dev->stats.rx_errors++; + kfree(out); }
static int ppp_rx(struct sk_buff *skb)