From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC1F4C00144 for ; Mon, 1 Aug 2022 18:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233818AbiHASZk (ORCPT ); Mon, 1 Aug 2022 14:25:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58530 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233535AbiHASZe (ORCPT ); Mon, 1 Aug 2022 14:25:34 -0400 Received: from mail-pf1-x44a.google.com (mail-pf1-x44a.google.com [IPv6:2607:f8b0:4864:20::44a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84FE3286DF for ; Mon, 1 Aug 2022 11:25:33 -0700 (PDT) Received: by mail-pf1-x44a.google.com with SMTP id x193-20020a6286ca000000b0052d47405364so1243620pfd.13 for ; Mon, 01 Aug 2022 11:25:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:mime-version:message-id:date:from:to:cc; bh=3ngPVFbWLrNVJ91bCrd9T752zLcOTxZPhTLYHqaFcYE=; b=ebYFDd/GgVOBe+QvOvCevnyUH1nc4rURICgSapFdHelYdD/z4J31GhJgQjpdGFKg8q UiI51K30y8baUw7vd9DbjIgsuy5oVkQY0UdEHUIok/NjrC+HeE994jqnbfQWKDUv7MmA hOf2qnD69491ZGU7QHDrCee1ZDhEi+1MaoDj2RTIK/ogF30kQVSQ91fuTPrqkZ9DtaRj O8UjcKs3NtGyJ4KyDZ0NhXQYjR9Uh+tTa/ixGFrAoi+2sGIPa1hNk6qCN4WcRYauPO7v 2+pJpfHeAuEgaP45nDDJpHiuF34opsqpjxxgwYL71KGilofqRLpb8Hzzr4fc0glLtFI+ Tz1w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:mime-version:message-id:date:x-gm-message-state :from:to:cc; bh=3ngPVFbWLrNVJ91bCrd9T752zLcOTxZPhTLYHqaFcYE=; b=vvn62PEV6mSYwOy3zC1i8YQp+BNXg45x4qZZ1SBRRgxEPnbayLPcsuvYzycgRUxu4b BR/D4EVHvJRs4u/9XVKqqr0XvqONz3VbvGEiwHGHRoUtRd6q3GcY/+v03+1u0/53fVu7 1aVNnE1A1QwYdG9xlV44+Sp41AZSCSDtyMNL44Q2J6+KloqajQQShj7ms2FEYQzlbpYa ntAbpc3p6yos3Y9vF4IG93/JdrMgp6JiEjj4V/b+nlzmN8btRPFy0bKMgoQyj56vgI78 yLd2e8nm5/Pj8cir1UyPYo5/+ixflQqkBfMt6w3TfCjB4NKz2JRmdn8OxuRb1J0ExgKR HKYg== X-Gm-Message-State: AJIora/TOGsloXZKKnkunUA8MDs9rkdNmFCNKraQNbq9v8aoholVetwU 8HGDkGvsORoudr2wxfG2fxpGxOo2rNjtNg== X-Google-Smtp-Source: AGRyM1uzSNxcGnj8jzcFfCx0ct2wm/QGuxQ8s+CT7r9NxsfM3tFH8d74S5zEw3l4d8hBSkgt7o5foqP0XeuamA== X-Received: from zllamas.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:4c]) (user=cmllamas job=sendgmr) by 2002:a63:f74e:0:b0:41a:716c:bfc4 with SMTP id f14-20020a63f74e000000b0041a716cbfc4mr14157055pgk.14.1659378333093; Mon, 01 Aug 2022 11:25:33 -0700 (PDT) Date: Mon, 1 Aug 2022 18:25:11 +0000 Message-Id: <20220801182511.3371447-1-cmllamas@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.37.1.455.g008518b4e5-goog Subject: [PATCH] binder: fix UAF of ref->proc caused by race condition From: Carlos Llamas To: Greg Kroah-Hartman , "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" , Todd Kjos , Martijn Coenen , Christian Brauner Cc: Joel Fernandes , Suren Baghdasaryan , kernel-team@android.com, linux-kernel@vger.kernel.org, Carlos Llamas Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A transaction of type BINDER_TYPE_WEAK_HANDLE can fail to increment the reference for a node. In this case, the target proc normally releases the failed reference upon close as expected. However, if the target is dying in parallel the call will race with binder_deferred_release(), so the target could have released all of its references by now leaving the cleanup of the new failed reference unhandled. The transaction then ends and the target proc gets released making the ref->proc now a dangling pointer. Later on, ref->node is closed and we attempt to take spin_lock(&ref->proc->inner_lock), which leads to the use-after-free bug reported below. Let's fix this by cleaning up the failed reference on the spot instead of relying on the target to do so. ================================================================== BUG: KASAN: use-after-free in _raw_spin_lock+0xa8/0x150 Write of size 4 at addr ffff5ca207094238 by task kworker/1:0/590 CPU: 1 PID: 590 Comm: kworker/1:0 Not tainted 5.19.0-rc8 #10 Hardware name: linux,dummy-virt (DT) Workqueue: events binder_deferred_func Call trace: dump_backtrace.part.0+0x1d0/0x1e0 show_stack+0x18/0x70 dump_stack_lvl+0x68/0x84 print_report+0x2e4/0x61c kasan_report+0xa4/0x110 kasan_check_range+0xfc/0x1a4 __kasan_check_write+0x3c/0x50 _raw_spin_lock+0xa8/0x150 binder_deferred_func+0x5e0/0x9b0 process_one_work+0x38c/0x5f0 worker_thread+0x9c/0x694 kthread+0x188/0x190 ret_from_fork+0x10/0x20 Signed-off-by: Carlos Llamas --- drivers/android/binder.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 362c0deb65f1..9d42afe60180 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -1361,6 +1361,18 @@ static int binder_inc_ref_for_node(struct binder_proc *proc, } ret = binder_inc_ref_olocked(ref, strong, target_list); *rdata = ref->data; + if (ret && ref == new_ref) { + /* + * Cleanup the failed reference here as the target + * could now be dead and have already released its + * references by now. Calling on the new reference + * with strong=0 and a tmp_refs will not decrement + * the node. The new_ref gets kfree'd below. + */ + binder_cleanup_ref_olocked(new_ref); + ref = NULL; + } + binder_proc_unlock(proc); if (new_ref && ref != new_ref) /* -- 2.37.1.455.g008518b4e5-goog