From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f71.google.com (mail-oa1-f71.google.com [209.85.160.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0A0138BF9A for ; Sun, 30 Aug 2026 07:57:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788076642; cv=none; b=jAyHDcJDd5bY+1Dz24xe/uVWn1MzjHv7GWrnS4K586iCVH5ITpXjza3FW+v8155LDfs7o3KjkmvfNR76MVfWnGMH6zF6wvKIaInwjlcVQSlx9Y6SHegJWgR+zQSdt03kmr+aEBlC9YhwJB8uvDXq9kVqJO+Xwi5dOzuu/QERATo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788076642; c=relaxed/simple; bh=qdgOvI9ZfoXBgad9Bu6vpvpaB75XjF0VCfNp3WoOhk4=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To:Cc: Content-Type; b=LZv2RBvuKziMM/AXOl3p1+WF1wWOkTLpxcyiBUJKw65qTKKgqu7KFHnJyCGIQs1A66VnQKWq9nCN79fmH6i4NSw4kpgzBwbWQ/LRJERWy04RJm4mRVZHqCRnprbQw0KU1Xo140muXXwqHF4+ZJdnO1tTTTT2QjXBsndPgZLD/8M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.160.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oa1-f71.google.com with SMTP id 586e51a60fabf-4667f641a98so3517506fac.1 for ; Sun, 30 Aug 2026 00:57:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788076639; x=1788681439; h=content-type:cc:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=IyWKVtx2DmQgfl0T4AIbgWKHxP9LYOliY6XtyNUqPz8=; b=C8KfzQOvqrQxo2ldLioVUe9hVW//l8YGMjWqQQ2xebPC+Ikq7H8lCwmleetZNAWWor pnJ4XGohG5yKnC/zKASPXd2np5P5+am1NGabXXWprazxaukTtV26p1hQPgFTV3758jZi 8UL4CV3ILgMpzWfuvKQ1GJ6aL6wQif6yjz+gQHzV8Fzoiq6Hwbx4qZGQYuidsel+fYJY 0A6I8lL/N2HPa/vkzlWNfQnLLszr4sNHnsryWmHAar0cuTS44D896BmbFnzHti13e93R KrJjkFAuhyCsLLHC83QMY3EjLSS6zne8dKG03ZJ803KI7p7sqrrn2DQLDQLGRqKBXZLN klDw== X-Forwarded-Encrypted: i=1; AHgh+Ro/Z6PHCHChDDSLbyfZyJp6WM6dDgYKQQnymbk5AlbM/nNNeKC8Bbw6AQG/ArVz6BwYzwQ5r5C10AHPyI4=@vger.kernel.org X-Gm-Message-State: AFuF++kqHPMTiZCPZivdpNn+fA6GPnLiPzYDDRqPC1/gCE2bL83fHD/B y3WYfngG3ekugvK5DeMyRYNn4FCqTGfFOClRBE6OCehSvCRHrwMnhJQ9/xyYfsGg0odXwwTE2uC 4a/cTH0kbEcAQ3y5KYOkrY7M4LgZ5gC+GiBq+gV2wP7wOSnwxDTKIXSLikAE= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1f06:b0:6b1:3663:8616 with SMTP id 006d021491bc7-6b1c679f21cmr17021769eaf.33.1788076639666; Sun, 30 Aug 2026 00:57:19 -0700 (PDT) Date: Sun, 30 Aug 2026 00:57:19 -0700 In-Reply-To: <20260830075708.16258-1-kartikey406@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a93e25f.1d9ded08.62e62.0118.GAE@google.com> Subject: Re: [PATCH] media: vidtv: fix mutex use-after-destroy in vidtv_bridge_remove() From: syzbot To: kartikey406@gmail.com Cc: kartikey406@gmail.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" > #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master This crash does not have a reproducer. I cannot test it. > > > mutex_destroy(&dvb->feed_lock) is called too early in > vidtv_bridge_remove(), before dvb_dmxdev_release() and > dvb_dmx_release(). Both of these can still trigger vidtv_stop_feed(), > which locks feed_lock, causing DEBUG_LOCKS_WARN_ON(lock->magic != > lock) in __mutex_lock(). > > Fix by moving mutex_destroy() to after dvb_dmxdev_release() and > dvb_dmx_release() return, and by stopping any active streaming under > feed_lock beforehand so a late vidtv_stop_feed() call sees > dvb->streaming == false and returns early. > > Reported-by: syzbot+3157015c6bd85395cddc@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3157015c6bd85395cddc > Signed-off-by: Deepanshu Kartikey > --- > drivers/media/test-drivers/vidtv/vidtv_bridge.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c > index fd69b4ee16f4..6bebf4617100 100644 > --- a/drivers/media/test-drivers/vidtv/vidtv_bridge.c > +++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c > @@ -548,7 +548,14 @@ static void vidtv_bridge_remove(struct platform_device *pdev) > media_device_cleanup(&dvb->mdev); > #endif /* CONFIG_MEDIA_CONTROLLER_DVB */ > > - mutex_destroy(&dvb->feed_lock); > + mutex_lock(&dvb->feed_lock); > + if (dvb->streaming) { > + dvb->streaming = false; > + vidtv_mux_stop_thread(dvb->mux); > + vidtv_mux_destroy(dvb->mux); > + dvb->mux = NULL; > + } > + mutex_unlock(&dvb->feed_lock); > > for (i = 0; i < NUM_FE; ++i) { > dvb_unregister_frontend(dvb->fe[i]); > @@ -559,6 +566,9 @@ static void vidtv_bridge_remove(struct platform_device *pdev) > dvb_dmxdev_release(&dvb->dmx_dev); > dvb_dmx_release(&dvb->demux); > dvb_unregister_adapter(&dvb->adapter); > + > + mutex_destroy(&dvb->feed_lock); > + > dev_info(&pdev->dev, "Successfully removed vidtv\n"); > } > > -- > 2.43.0 >