From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx01.bremer-it.com (mx01.bremer-it.com [85.215.132.167]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 02E85318EC5; Sat, 19 Sep 2026 14:22:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=85.215.132.167 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789827728; cv=none; b=gXxuQ9J5IX8ejrlc8GKEo1bDFTakZ7/0XtJRwiQPlKcDHWxTpGqO9rIuNj3FReo61q3sVh1BgiqDzjrMpQc6bcD7+vu3McuAuosObJKQdghOYlGqQHxowFAlhex5aYUh3kKQR2EqJTxkkgtWBPc0gPCf3qT6UI0FiQC7qsU+agE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789827728; c=relaxed/simple; bh=rNl+6nbewWw93Wpe/5vUB10fe3mgwVH21uAmleOoZuU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fLwOEfmfpXh+okDzTgCv8a4UWve0h2brWkNhAuSF+1Ce2V8+StRLcOWOMEGMcRksEVj+cu38242L9q8vmFT7eOgY6mTBwXZ8NcS/kE6CbGKq3OhxY9dZY8H5HC5TY4NYs7kri3yQ8CIYtvnGOawXpZH2oLDV4fFQPPZxOKPW7B4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=barelysecure.org; spf=pass smtp.mailfrom=barelysecure.org; dkim=pass (2048-bit key) header.d=barelysecure.org header.i=@barelysecure.org header.b=W6h9jXQc; arc=none smtp.client-ip=85.215.132.167 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=barelysecure.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=barelysecure.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=barelysecure.org header.i=@barelysecure.org header.b="W6h9jXQc" Received: from cashel.logfs.org (c-98-33-96-243.hsd1.ca.comcast.net [98.33.96.243]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature ECDSA (secp384r1) server-digest SHA384) (No client certificate requested) by mx01.bremer-it.com (Postfix) with ESMTPSA id 0C32020BD1; Sat, 19 Sep 2026 16:21:52 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=barelysecure.org; s=dkim68; t=1789827716; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dF0vvhSQmDb1GBoZeo34gbG9l05gqX6VJ3NyhVM0R2A=; b=W6h9jXQcxIeA/cFgWioUmhHjg4orfTMF/v1oPeAHiBz/3WHjJWeRCYD4Sn1OgRfBVHb67D 2I+3lwcnWxV5UtLkWfuFF3FoYkdNJUgCR4qK9vt3IwZuK2O1/F2x4ngyIbTs7nr1jbyWbo KU7Ynp2ZN3qQ9Uw01+NrtRkbdrxi9ILCEi0ZUv0EzO0+Iz87iigWYBESqjxuE5AvTAYl1M nb9BeYxk6tNxmMafU3FwUUVYvllh7Dq80MjJjtvgozNGcjonE0YDKc6bjBwQ7D5sNamTyn zX34VZzpRJkhTi9iqo8hGQTwAsdumqtUTtr8Ir55/1kjAsAazVpoKtqYQwhqOQ== Authentication-Results: ORIGINATING; auth=pass smtp.auth=joern@lazybastard.org smtp.mailfrom=joern@barelysecure.org Date: Sat, 19 Sep 2026 07:21:50 -0700 From: =?iso-8859-1?Q?J=F6rn?= Engel To: Richard Weinberger Cc: Chris Roy , Greg KH , syzbot , dakr@kernel.org, driver-core@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, rafael@kernel.org, syzkaller-bugs@googlegroups.com, linux-mtd@lists.infradead.org, miquel.raynal@bootlin.com, vigneshr@ti.com, Adarsh Das Subject: Re: AW: [syzbot] [fs?] possible deadlock in ovl_create_object (2) Message-ID: References: <6aab0f82.e91c2013.3bdb06.0009.GAE@google.com> <2026091753-broadness-bootie-b683@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spam-Level: * X-Rspamd-Action: no action X-Spamd-Result: default: False [1.40 / 14.00]; SUSPICIOUS_RECIPS(1.50)[]; MIME_GOOD(-0.10)[text/plain]; BAYES_HAM(-0.00)[17.57%]; RCVD_COUNT_ZERO(0.00)[0]; ARC_NA(0.00)[]; TAGGED_RCPT(0.00)[7cab6a19619f1b8efc00]; ASN(0.00)[asn:7922, ipnet:98.32.0.0/11, country:US]; MIME_TRACE(0.00)[0:+]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[14]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[barelysecure.org:s=dkim68]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; ALIAS_RESOLVED(0.00)[]; LOCAL_OUTBOUND(0.00)[]; FREEMAIL_CC(0.00)[thechris.in,linuxfoundation.org,syzkaller.appspotmail.com,kernel.org,lists.linux.dev,vger.kernel.org,googlegroups.com,lists.infradead.org,bootlin.com,ti.com,gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; URIBL_BLOCKED(0.00)[barelysecure.org:from_smtp,barelysecure.org:from_mime,c-98-33-96-243.hsd1.ca.comcast.net:rdns]; SUBJECT_HAS_QUESTION(0.00)[] X-Rspamd-Server: server01 X-Rspamd-Queue-Id: 0C32020BD1 X-Spamd-Bar: + I added Adarsh Das, who also attempted to fix this bug. On Sat, Sep 19, 2026 at 07:42:25AM +0000, Richard Weinberger wrote: > > While we're here, maybe it's time to add a decent configfs interface to > this driver instead of configuring through module parameters. > That way also multiple instances are possible. I honestly wonder whether this driver has any production users. It is somewhat useful for developers that want to simulate hardware they don't have. But beyond that? Anyway, I have two deeper review questions as well. One, afaics block2mtd predates overlayfs. If the bug requires the interaction of both, it is overlayfs that introduced the bug. So why do we fix it by modifying block2mtd? Is that really the appropriate way to fix it? Two, we fix the deadlock by adding a second thread (via workqueue). But to keep synchronous behavior we end up blocking until the second thread has finished. Does the blocking behavior recreate a circular dependency and therefore a deadlock? If not, why not? Jörn -- Prosperity makes friends, adversity tries them. -- Publilius Syrus