EDB-ID: 41791 | Author: Google Security Research | Published: 2017-04-04 | CVE: CVE-2017-2472 | Type: Dos | Platform: macOS | Aliases: N/A | Advisory/Source: Link | Tags: Denial of Service (DoS) | Vulnerable App: N/A | Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1104
exec_handle_port_actions is responsible for handling the xnu port actions extension to posix_spawn.
It supports 4 different types of port (PSPA_SPECIAL, PSPA_EXCEPTION, PSPA_AU_SESSION and PSPA_IMP_WATCHPORTS)
For the special, exception and audit ports it tries to update the new task to reflect the port action
by calling either task_set_special_port, task_set_exception_ports or audit_session_spawnjoin and if
any of those calls fail it calls ipc_port_release_send(port).
task_set_special_port and task_set_exception_ports don't drop a reference on the port if they fail
but audit_session_spawnjoin (which calls to audit_session_join_internal) *does* drop a reference on
the port on failure. It's easy to make audit_session_spawnjoin fail by specifying a port which isn't
an audit session port.
This means we can cause two references to be dropped on the port when only one is held leading to a
use after free in the kernel.
Tested on MacOS 10.12.3 (16D32) on MacBookAir5,2
*/
// ianbeer
#if 0
MacOS/iOS kernel uaf due to double-release in posix_spawn
exec_handle_port_actions is responsible for handling the xnu port actions extension to posix_spawn.
It supports 4 different types of port (PSPA_SPECIAL, PSPA_EXCEPTION, PSPA_AU_SESSION and PSPA_IMP_WATCHPORTS)
For the special, exception and audit ports it tries to update the new task to reflect the port action
by calling either task_set_special_port, task_set_exception_ports or audit_session_spawnjoin and if
any of those calls fail it calls ipc_port_release_send(port).
task_set_special_port and task_set_exception_ports don't drop a reference on the port if they fail
but audit_session_spawnjoin (which calls to audit_session_join_internal) *does* drop a reference on
the port on failure. It's easy to make audit_session_spawnjoin fail by specifying a port which isn't
an audit session port.
This means we can cause two references to be dropped on the port when only one is held leading to a
use after free in the kernel.
Tested on MacOS 10.12.3 (16D32) on MacBookAir5,2
