From: Marcel Holtmann marcel@holtmann.org
[ Upstream commit 7c9cbd0b5e38a1672fcd137894ace3b042dfbf69 ]
The function l2cap_get_conf_opt will return L2CAP_CONF_OPT_SIZE + opt->len as length value. The opt->len however is in control over the remote user and can be used by an attacker to gain access beyond the bounds of the actual packet.
To prevent any potential leak of heap memory, it is enough to check that the resulting len calculation after calling l2cap_get_conf_opt is not below zero. A well formed packet will always return >= 0 here and will end with the length value being zero after the last option has been parsed. In case of malformed packets messing with the opt->len field the length value will become negative. If that is the case, then just abort and ignore the option.
In case an attacker uses a too short opt->len value, then garbage will be parsed, but that is protected by the unknown option handling and also the option parameter size checks.
Signed-off-by: Marcel Holtmann marcel@holtmann.org Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Johan Hedberg johan.hedberg@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/l2cap_core.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 9b7907ebfa01..7a8a58af8c98 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -3336,6 +3336,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
while (len >= L2CAP_CONF_OPT_SIZE) { len -= l2cap_get_conf_opt(&req, &type, &olen, &val); + if (len < 0) + break;
hint = type & L2CAP_CONF_HINT; type &= L2CAP_CONF_MASK; @@ -3547,6 +3549,8 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len,
while (len >= L2CAP_CONF_OPT_SIZE) { len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val); + if (len < 0) + break;
switch (type) { case L2CAP_CONF_MTU: @@ -3727,6 +3731,8 @@ static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len)
while (len >= L2CAP_CONF_OPT_SIZE) { len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val); + if (len < 0) + break;
switch (type) { case L2CAP_CONF_RFC: