This is a note to let you know that I've just added the patch titled

Bluetooth: Prevent stack info leak from the EFS element.

to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 06e7e776ca4d36547e503279aeff996cbb292c16 Mon Sep 17 00:00:00 2001

From: Ben Seri ben@armis.com Date: Fri, 8 Dec 2017 15:14:47 +0100 Subject: Bluetooth: Prevent stack info leak from the EFS element.

In the function l2cap_parse_conf_rsp and in the function l2cap_parse_conf_req the following variable is declared without initialization:

struct l2cap_conf_efs efs;

In addition, when parsing input configuration parameters in both of these functions, the switch case for handling EFS elements may skip the memcpy call that will write to the efs variable:

... case L2CAP_CONF_EFS: if (olen == sizeof(efs)) memcpy(&efs, (void *)val, olen); ...

The olen in the above if is attacker controlled, and regardless of that if, in both of these functions the efs variable would eventually be added to the outgoing configuration request that is being built:

l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs), (unsigned long) &efs);

So by sending a configuration request, or response, that contains an L2CAP_CONF_EFS element, but with an element length that is not sizeof(efs) - the memcpy to the uninitialized efs variable can be avoided, and the uninitialized variable would be returned to the attacker (16 bytes).

This issue has been assigned CVE-2017-1000410

Cc: Marcel Holtmann marcel@holtmann.org Cc: Gustavo Padovan gustavo@padovan.org Cc: Johan Hedberg johan.hedberg@gmail.com Cc: stable stable@vger.kernel.org Signed-off-by: Ben Seri ben@armis.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bluetooth/l2cap_core.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 43ba91c440bc..fc6615d59165 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -3363,9 +3363,10 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data break;

case L2CAP_CONF_EFS: - remote_efs = 1; - if (olen == sizeof(efs)) + if (olen == sizeof(efs)) { + remote_efs = 1; memcpy(&efs, (void *) val, olen); + } break;

case L2CAP_CONF_EWS: @@ -3584,16 +3585,17 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len, break;

case L2CAP_CONF_EFS: - if (olen == sizeof(efs)) + if (olen == sizeof(efs)) { memcpy(&efs, (void *)val, olen);

- if (chan->local_stype != L2CAP_SERV_NOTRAFIC && - efs.stype != L2CAP_SERV_NOTRAFIC && - efs.stype != chan->local_stype) - return -ECONNREFUSED; + if (chan->local_stype != L2CAP_SERV_NOTRAFIC && + efs.stype != L2CAP_SERV_NOTRAFIC && + efs.stype != chan->local_stype) + return -ECONNREFUSED;

- l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs), - (unsigned long) &efs, endptr - ptr); + l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs), + (unsigned long) &efs, endptr - ptr); + } break;

case L2CAP_CONF_FCS: