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.
Fixes: d579b04a52a1 ("binder: frozen notification")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
---
drivers/android/binder.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 4d90203ea048..8bca2de6fa24 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -5593,6 +5593,8 @@ static void binder_add_freeze_work(struct binder_proc *proc, bool is_frozen)
prev = node;
binder_node_unlock(node);
binder_inner_proc_lock(proc);
+ if (proc->is_dead)
+ break;
}
binder_inner_proc_unlock(proc);
if (prev)
--
2.46.0.792.g87dc391469-goog
