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.

Affected Software

References

• https://git.kernel.org/stable/c/011e69a1b23011c0db3af4b8293fdd4522cc97b0
• https://git.kernel.org/stable/c/6b1be1da1f8279cf091266e71b5153c5b02aaff6