CVE-2024-56555

In the Linux kernel, the following vulnerability has been resolved:

binder: fix OOB in binder_add_freeze_work()

In binder_add_freeze_work() we iterate over the proc->nodes with the

proc->inner_lock held. However, this lock is temporarily dropped to

acquire the node->lock first (lock nesting order). This can race with

binder_deferred_release() which removes the nodes from the proc->nodes

rbtree and adds them into binder_dead_nodes list. This leads to a broken

iteration in binder_add_freeze_work() as rb_next() will use data from

binder_dead_nodes, triggering an out-of-bounds access:

==================================================================

BUG: KASAN: global-out-of-bounds in rb_next+0xfc/0x124

Read of size 8 at addr ffffcb84285f7170 by task freeze/660

CPU: 8 UID: 0 PID: 660 Comm: freeze Not tainted 6.11.0-07343-ga727812a8d45 #18

Hardware name: linux,dummy-virt (DT)

Call trace:

rb_next+0xfc/0x124

binder_add_freeze_work+0x344/0x534

binder_ioctl+0x1e70/0x25ac

__arm64_sys_ioctl+0x124/0x190

The buggy address belongs to the variable:

binder_dead_nodes+0x10/0x40

[...]

==================================================================

This is possible because proc->nodes (rbtree) and binder_dead_nodes

(list) share entries in binder_node through a union:

struct binder_node {

[...]

union {

struct rb_node rb_node;

struct hlist_node dead_node;

};

Fix the race by checking that the proc is still alive. If not, simply

break out of the iteration.