Ilya Maximets <[email protected]> writes: > The push_nsh() action structure looks like this: > > OVS_ACTION_ATTR_PUSH_NSH(OVS_KEY_ATTR_NSH(OVS_NSH_KEY_ATTR_BASE,...)) > > The outermost OVS_ACTION_ATTR_PUSH_NSH attribute is OK'ed by the > nla_for_each_nested() inside __ovs_nla_copy_actions(). The innermost > OVS_NSH_KEY_ATTR_BASE/MD1/MD2 are OK'ed by the nla_for_each_nested() > inside nsh_key_put_from_nlattr(). But nothing checks if the attribute > in the middle is OK. We don't even check that this attribute is the > OVS_KEY_ATTR_NSH. We just do a double unwrap with a pair of nla_data() > calls - first time directly while calling validate_push_nsh() and the > second time as part of the nla_for_each_nested() macro, which isn't > safe, potentially causing invalid memory access if the size of this > attribute is incorrect. The failure may not be noticed during > validation due to larger netlink buffer, but cause trouble later during > action execution where the buffer is allocated exactly to the size: > > BUG: KASAN: slab-out-of-bounds in nsh_hdr_from_nlattr+0x1dd/0x6a0 > [openvswitch] > Read of size 184 at addr ffff88816459a634 by task a.out/22624 > > CPU: 8 UID: 0 PID: 22624 6.18.0-rc7+ #115 PREEMPT(voluntary) > Call Trace: > <TASK> > dump_stack_lvl+0x51/0x70 > print_address_description.constprop.0+0x2c/0x390 > kasan_report+0xdd/0x110 > kasan_check_range+0x35/0x1b0 > __asan_memcpy+0x20/0x60 > nsh_hdr_from_nlattr+0x1dd/0x6a0 [openvswitch] > push_nsh+0x82/0x120 [openvswitch] > do_execute_actions+0x1405/0x2840 [openvswitch] > ovs_execute_actions+0xd5/0x3b0 [openvswitch] > ovs_packet_cmd_execute+0x949/0xdb0 [openvswitch] > genl_family_rcv_msg_doit+0x1d6/0x2b0 > genl_family_rcv_msg+0x336/0x580 > genl_rcv_msg+0x9f/0x130 > netlink_rcv_skb+0x11f/0x370 > genl_rcv+0x24/0x40 > netlink_unicast+0x73e/0xaa0 > netlink_sendmsg+0x744/0xbf0 > __sys_sendto+0x3d6/0x450 > do_syscall_64+0x79/0x2c0 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > </TASK> > > Let's add some checks that the attribute is properly sized and it's > the only one attribute inside the action. Technically, there is no > real reason for OVS_KEY_ATTR_NSH to be there, as we know that we're > pushing an NSH header already, it just creates extra nesting, but > that's how uAPI works today. So, keeping as it is. > > Fixes: b2d0f5d5dc53 ("openvswitch: enable NSH support") > Reported-by: Junvy Yang <[email protected]> > Signed-off-by: Ilya Maximets <[email protected]> > ---
Checked it out using also the userspace kmod test suite, and the kernel selftest scripts. Change makes sense to me. Reviewed-by: Aaron Conole <[email protected]> _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
