Re: [PATCH v2 7/8] binder: fix memleak of proc->delivered_freeze

[Todd Kjos <tkjos@google.com>]

On Thu, Sep 26, 2024 at 4:37 PM Carlos Llamas <cmllamas@google.com> wrote:
>
> If a freeze notification is cleared with BC_CLEAR_FREEZE_NOTIFICATION
> before calling binder_freeze_notification_done(), then it is detached
> from its reference (e.g. ref->freeze) but the work remains queued in
> proc->delivered_freeze. This leads to a memory leak when the process
> exits as any pending entries in proc->delivered_freeze are not freed:
>
>   unreferenced object 0xffff38e8cfa36180 (size 64):
>     comm "binder-util", pid 655, jiffies 4294936641
>     hex dump (first 32 bytes):
>       b8 e9 9e c8 e8 38 ff ff b8 e9 9e c8 e8 38 ff ff  .....8.......8..
>       0b 00 00 00 00 00 00 00 3c 1f 4b 00 00 00 00 00  ........<.K.....
>     backtrace (crc 95983b32):
>       [<000000000d0582cf>] kmemleak_alloc+0x34/0x40
>       [<000000009c99a513>] __kmalloc_cache_noprof+0x208/0x280
>       [<00000000313b1704>] binder_thread_write+0xdec/0x439c
>       [<000000000cbd33bb>] binder_ioctl+0x1b68/0x22cc
>       [<000000002bbedeeb>] __arm64_sys_ioctl+0x124/0x190
>       [<00000000b439adee>] invoke_syscall+0x6c/0x254
>       [<00000000173558fc>] el0_svc_common.constprop.0+0xac/0x230
>       [<0000000084f72311>] do_el0_svc+0x40/0x58
>       [<000000008b872457>] el0_svc+0x38/0x78
>       [<00000000ee778653>] el0t_64_sync_handler+0x120/0x12c
>       [<00000000a8ec61bf>] el0t_64_sync+0x190/0x194
>
> This patch fixes the leak by ensuring that any pending entries in
> proc->delivered_freeze are freed during binder_deferred_release().
>
> Fixes: d579b04a52a1 ("binder: frozen notification")
> Cc: stable@vger.kernel.org
> Signed-off-by: Carlos Llamas <cmllamas@google.com>

Acked-by: Todd Kjos <tkjos@google.com>

> ---
>  drivers/android/binder.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 415fc9759249..7c09b5e38e32 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -5155,6 +5155,16 @@ static void binder_release_work(struct binder_proc *proc,
>                 } break;
>                 case BINDER_WORK_NODE:
>                         break;
> +               case BINDER_WORK_CLEAR_FREEZE_NOTIFICATION: {
> +                       struct binder_ref_freeze *freeze;
> +
> +                       freeze = container_of(w, struct binder_ref_freeze, work);
> +                       binder_debug(BINDER_DEBUG_DEAD_TRANSACTION,
> +                                    "undelivered freeze notification, %016llx\n",
> +                                    (u64)freeze->cookie);
> +                       kfree(freeze);
> +                       binder_stats_deleted(BINDER_STAT_FREEZE);
> +               } break;
>                 default:
>                         pr_err("unexpected work type, %d, not freed\n",
>                                wtype);
> @@ -6273,6 +6283,7 @@ static void binder_deferred_release(struct binder_proc *proc)
>
>         binder_release_work(proc, &proc->todo);
>         binder_release_work(proc, &proc->delivered_death);
> +       binder_release_work(proc, &proc->delivered_freeze);
>
>         binder_debug(BINDER_DEBUG_OPEN_CLOSE,
>                      "%s: %d threads %d, nodes %d (ref %d), refs %d, active transactions %d\n",
> --
> 2.46.1.824.gd892dcdcdd-goog
>