CVE-2017-1000410

The Linux kernel version 3.3-rc1 and later is affected by a vulnerability
lies in the processing of incoming L2CAP commands - ConfigRequest, and
ConfigResponse messages. This info leak is a result of uninitialized stack
variables that may be returned to an attacker in their uninitialized state.
By manipulating the code flows that precede the handling of these
configuration messages, an attacker can also gain some control over which
data will be held in the uninitialized stack variables. This can allow him
to bypass KASLR, and stack canaries protection - as both pointers and stack
canaries may be leaked in this manner. Combining this vulnerability (for
example) with the previously disclosed RCE vulnerability in L2CAP
configuration parsing (CVE-2017-1000251) may allow an attacker to exploit
the RCE against kernels which were built with the above mitigations. These
are the specifics of this vulnerability: 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).