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 F0399C4332F for ; Mon, 28 Nov 2022 16:23:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232778AbiK1QXG (ORCPT ); Mon, 28 Nov 2022 11:23:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232725AbiK1QWt (ORCPT ); Mon, 28 Nov 2022 11:22:49 -0500 Received: from zju.edu.cn (spam.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3C3ED2098B; Mon, 28 Nov 2022 08:22:35 -0800 (PST) Received: from zju.edu.cn (unknown [10.12.77.33]) by mail-app2 (Coremail) with SMTP id by_KCgB3J2go4IRjlapJCA--.26077S4; Tue, 29 Nov 2022 00:22:00 +0800 (CST) From: Lin Ma To: mchehab@kernel.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Lin Ma , syzbot+fce48a3dd3368645bd6c@syzkaller.appspotmail.com Subject: [PATCH v0] media: dvbdev: fix refcnt bug Date: Tue, 29 Nov 2022 00:21:59 +0800 Message-Id: <20221128162159.16901-1-linma@zju.edu.cn> X-Mailer: git-send-email 2.38.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID: by_KCgB3J2go4IRjlapJCA--.26077S4 X-Coremail-Antispam: 1UD129KBjvJXoWxJr45KFyrCw4rKFyfuF43trb_yoW5JFy8pa yUGFyYkrW8Kr1xJr4UAw1UJr15Jw4vyFy8Jry7Xr1DtF17Gw1UJr1jyrWUAryDJrs7Zr17 tr1UWwn2vr4DWaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkv1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2 z280aVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gr1j6F4UJwAS0I0E0x vYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AK xVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48Icx kI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwCF04k20xvY0x0EwIxGrwCF04k20xvE 74AGY7Cv6cx26r4fKr1UJr1l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxV WUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r126r1DMIIYrxkI 7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r 1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI 42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x0JUdHUDUUUUU= X-CM-SenderInfo: qtrwiiyqvtljo62m3hxhgxhubq/ Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Previous commit initialize the dvbdev->ref before the template copy, which will overwrite the reference and cause refcnt bug. refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 1 at lib/refcount.c:25 refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25 Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc6-next-20221128-syzkaller #0 ... RIP: 0010:refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25 RSP: 0000:ffffc900000678d0 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88813ff58000 RSI: ffffffff81660e7c RDI: fffff5200000cf0c RBP: ffff888022a45010 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000080000000 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff88823ffff000 CR3: 000000000c48e000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_add include/linux/refcount.h:199 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] kref_get include/linux/kref.h:45 [inline] dvb_device_get drivers/media/dvb-core/dvbdev.c:585 [inline] dvb_register_device+0xe83/0x16e0 drivers/media/dvb-core/dvbdev.c:517 ... Just place the kref_init at correct position. Reported-by: syzbot+fce48a3dd3368645bd6c@syzkaller.appspotmail.com Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF") Signed-off-by: Lin Ma --- drivers/media/dvb-core/dvbdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c index d45673cb3..2a857cf70 100644 --- a/drivers/media/dvb-core/dvbdev.c +++ b/drivers/media/dvb-core/dvbdev.c @@ -482,8 +482,8 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev, return -ENOMEM; } - kref_init(&dvbdev->ref); memcpy(dvbdev, template, sizeof(struct dvb_device)); + kref_init(&dvbdev->ref); dvbdev->type = type; dvbdev->id = id; dvbdev->adapter = adap; -- 2.38.1