From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=18.9.28.11 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793832969; b=rInYJlahNn5hzWDT4UOqPPq8OcGeTS5/015sXFV12GcWlEecp7LaNXAxbvQJp57Jvz2K JhM8HKPdtk+0We+Z1g3QYF5eaM68WsxI1yGHZwyVOAIU8kIY21WKtHGaaLh/12fDqclX5 oKIegPUSYBZLziH3Bw1y4DMALdiI2WNOELbduaGvWqUO6T9Z2rhVPI9+cNHxzOREhhOXp AC5sp4DDCrkCq6oImDHD9klEa/ibO5zAaaz6adtIv5+6mnjLZBlMRBzq09+6Mt8UCwslK X8iCkx6q6bXTno53WM9n5BY+ZJ6exn0TP+atcQaiYLWJlmqKuLnnVhn1WXXpjT7CY/A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793832969; h=DMARC-Filter:Received:DKIM-Signature:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=jHWBIHfHZnm3krj+u+UJd5sE5nCuIj9CeMaueCCID+U=; b=cMCYCjv0FhCE0ZBYc3ajoeJK1nAuyPz1bmGFu6YMfBitfQd5Ps2Q0jTCtbWsOsaXULhP iIYsY4xdtKWs8YM0PYMUZepbQkb8zGELCqqpYBTCDSdCOEdaCldqcPLNffd6vgyxKKMn1 iFoCRfcESY9LrSPf1mpJFVciPovoTRW4k+BNFs+KYHTPOlDMstvHFFIxhuv4KCG5Sgt2O SzoJDeh7+nTD7792fFFpF7itA5IAS8RSsIl48q3XNYmFoC3CC/76R7ce31oJvJ6j89hy0 ynEKJ2A/AT0a9SNpbZusSwmtORbGNocFbd2GmqEL1Xh6NPu6RlXudAn5/TC1MMo9j1w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=mit.edu; spf=pass smtp.mailfrom=mit.edu; dkim=pass header.d=mit.edu header.i=@mit.edu header.a=rsa-sha256 header.s=outgoing header.b="Ha3Y/erK"; arc=none smtp.remote-ip=18.9.28.11 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32F5C606A326 for ; Wed, 4 Nov 2026 22:56:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 32F5C606A326 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mit.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=mit.edu header.i=@mit.edu header.a=rsa-sha256 header.s=outgoing header.b=Ha3Y/erK Received: from macsyma.thunk.org (pool-173-48-116-148.bstnma.fios.verizon.net [173.48.116.148]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 6A4MtwHM008003 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 4 Nov 2026 17:55:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1793832960; bh=jHWBIHfHZnm3krj+u+UJd5sE5nCuIj9CeMaueCCID+U=; h=Date:From:Subject:Message-ID:MIME-Version:Content-Type; b=Ha3Y/erKQ+NqG18zFVhvkUzj6/Rx7Ydh1V40Jw86IjggGLR6f6EfcY9ENWPhAhqxU xAky+AnlNO5Jdxj+o2RKBgapBxEm5w2d6+xLpXnl+y7Z/z1G4cqB/O5+ZPAq+5rLhx EoEC1qmlg7J6gA6ThzazJ88suavEqvnMeSDkhKZ4yDQ7J4xiT6WuvhzJg0+qK2inRx imUkW7JDjFuy+m10vL721+RofqOZBUdsz+uoSlJPFzaQYuI4E/ugiH2+0uKHVjxuHs /Kp/cN+Y06k24qCMRdfzxccYe64ufnkDwKl+kq+/Nw94RyEZ5aRkZN5g5FQkzUxpYh y6kYQUiKSGe3g== Received: by macsyma.thunk.org (Postfix, from userid 15806) id 002F9253BC91; Wed, 4 Nov 2026 17:55:57 -0500 (EST) Date: Wed, 4 Nov 2026 17:55:57 -0500 From: "Theodore Tso" To: Bartos-Elekes Zsolt Cc: Eric Biggers , Andreas Dilger , linux-ext4@vger.kernel.org Subject: Re: PROBLEM: NULL pointer dereference in ext4_mb_load_buddy_gfp Message-ID: References: <6b2dbf1d-43b8-f9e9-a2b6-e538f295bf94@kite.hu> <20261103181757.GA2224825@google.com> X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Nov 03, 2026 at 08:47:21PM -0500, Bartos-Elekes Zsolt wrote: > Eric Biggers wrote: > > > On Tue, Nov 03, 2026 at 03:26:08PM +0100, Bartos-Elekes Zsolt wrote: > > > Linux version 6.1.191 (me@hostname) (gcc (Debian 12.2.0-14+deb12u1) 12.2.0, > > > > Yes, the stable maintainers broke ext4 in 6.1.191. The fix is > > https://lore.kernel.org/linux-ext4/20261102-ext4-ntfs3-null-folio-v1-1-4fd91ee23a4a@elliotjb.com/ Note that I *strongly* recommend that people use a kernel newer than 6.1 or 6.6. A lot of security fixes don't get backported to the older LTS kernels due to merge/cherry-pick conflicts, so your security team might be prohibiting or strongly disuading you from using such ancient LTS kernels. Furthermore, the "it builds, ship it" approach towards backporting fixes (including security fixes) is understandable, given the huge influx of fixes to AI-discovered security vulnerability. Unfortunately, it leads to frequent breakages to the older LTS kernels, and I no longer have time to debug ext4 failures to 6.1 and 6.6 LTS kernels. This is not to criticize those people who supply fixes to the 6.1 and 6.6 LTS kernels; in fact, I'm quite grateful for the people who do the work to support those older LTS kernels. And BTW, if someone is willing to be the ext4 stable backports maintainer for the older LTS kernels, and take on that responsibility in a more formal way. please contact me off-line. Cheers, - Ted P.S. It's not hard to monitor the 6.1-rc and 6.6-rc LTS kernels. That part is automated, and I can supply an e-mail feed of the automated runs of "gce-xfstests ltm -c ext4/all -g auto --repo stable-rc.git --watch linux-6.1.y" It's having a human being look at the huge number of test failures and notice when there are new failures (regressions), and then when there inevitably is a regression, doing the bisect to figure out which backport caused the failure is the thing I don't have time to do.