On Tue, Sep 24, 2024 at 11:44 AM Carlos Llamas <cmllamas@xxxxxxxxxx> wrote:
>
> 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>
Acked-by: Todd Kjos <tkjos@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
>
