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 in
> order to acquire the node->lock first (lock nesting order). This can
> race with binder_node_release() and trigger a use-after-free:
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in _raw_spin_lock+0xe4/0x19c
> Write of size 4 at addr ffff53c04c29dd04 by task freeze/640
>
> CPU: 5 UID: 0 PID: 640 Comm: freeze Not tainted 6.11.0-07343-ga727812a8d45 #17
> Hardware name: linux,dummy-virt (DT)
> Call trace:
> _raw_spin_lock+0xe4/0x19c
> binder_add_freeze_work+0x148/0x478
> binder_ioctl+0x1e70/0x25ac
> __arm64_sys_ioctl+0x124/0x190
>
> Allocated by task 637:
> __kmalloc_cache_noprof+0x12c/0x27c
> binder_new_node+0x50/0x700
> binder_transaction+0x35ac/0x6f74
> binder_thread_write+0xfb8/0x42a0
> binder_ioctl+0x18f0/0x25ac
> __arm64_sys_ioctl+0x124/0x190
>
> Freed by task 637:
> kfree+0xf0/0x330
> binder_thread_read+0x1e88/0x3a68
> binder_ioctl+0x16d8/0x25ac
> __arm64_sys_ioctl+0x124/0x190
> ==================================================================
>
> Fix the race by taking a temporary reference on the node before
> releasing the proc->inner lock. This ensures the node remains alive
> while in use.
>
> 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 | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 978740537a1a..4d90203ea048 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -5552,6 +5552,7 @@ static bool binder_txns_pending_ilocked(struct binder_proc *proc)
>
> static void binder_add_freeze_work(struct binder_proc *proc, bool is_frozen)
> {
> + struct binder_node *prev = NULL;
> struct rb_node *n;
> struct binder_ref *ref;
>
> @@ -5560,7 +5561,10 @@ static void binder_add_freeze_work(struct binder_proc *proc, bool is_frozen)
> struct binder_node *node;
>
> node = rb_entry(n, struct binder_node, rb_node);
> + binder_inc_node_tmpref_ilocked(node);
> binder_inner_proc_unlock(proc);
> + if (prev)
> + binder_put_node(prev);
> binder_node_lock(node);
> hlist_for_each_entry(ref, &node->refs, node_entry) {
> /*
> @@ -5586,10 +5590,13 @@ static void binder_add_freeze_work(struct binder_proc *proc, bool is_frozen)
> }
> binder_inner_proc_unlock(ref->proc);
> }
> + prev = node;
> binder_node_unlock(node);
> binder_inner_proc_lock(proc);
> }
> binder_inner_proc_unlock(proc);
> + if (prev)
> + binder_put_node(prev);
> }
>
> static int binder_ioctl_freeze(struct binder_freeze_info *info,
> --
> 2.46.0.792.g87dc391469-goog
>
