From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B1E78423149; Tue, 31 Mar 2026 16:54:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976070; cv=none; b=L/1Xt9B71yurF+7i3gWgvrXFVMInOAO9qTtF1hJFsCzKRIzmqVY62kZFPU8zZH77VGrYZbup3VEz++WPdzrI6+dEIsvWwBuG6LtGkGVDjVgUoBeZI8iip5jBDyO18h1s6yiK/2Y7thLbait4WIlurhU7X9exjhQ+ip5jn84KiAI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774976070; c=relaxed/simple; bh=DkNZK3DX7OTvmlLSUPfoNd1hgr0L+k8OdEpKUECWPaU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pJ5Tzj0cd57vKD0+khkcP42HtLrb0CsjQED+dO051PNvnLLv3Llp3SDdPfs80sM5M9FegTSHP7FhB8SMJDEb4cOfG770GST2k3CNq1GtQoVOevQ+7ltcM1sJCcG3vUlwZv+C5qZADq6dtEd+bsUTir04U9UBh5vFWSx6+2SLK2w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gWQ61184; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gWQ61184" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F2B2C19423; Tue, 31 Mar 2026 16:54:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774976070; bh=DkNZK3DX7OTvmlLSUPfoNd1hgr0L+k8OdEpKUECWPaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gWQ61184HFxfR6oi1tu8XbiPzwSwevscKZBmlSLBeicnbDoxMqdamuHma7/luwWA8 6DGuRuhmKtr3q8/BH4GIb61C3Mkj80ga5RvbPAjzFgbmP3CWLYQuz+X1E12NHo0BTE COVcZ+7Vof/psNY8mDEMAs6PUw8//1rKv8uF2dFs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Baokun Li , Theodore Tso , stable@kernel.org Subject: [PATCH 6.12 195/244] ext4: handle wraparound when searching for blocks for indirect mapped blocks Date: Tue, 31 Mar 2026 18:22:25 +0200 Message-ID: <20260331161748.951850225@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161741.651718120@linuxfoundation.org> References: <20260331161741.651718120@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit bb81702370fad22c06ca12b6e1648754dbc37e0f upstream. Commit 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") restricts what blocks will be allocated for indirect block based files to block numbers that fit within 32-bit block numbers. However, when using a review bot running on the latest Gemini LLM to check this commit when backporting into an LTS based kernel, it raised this concern: If ac->ac_g_ex.fe_group is >= ngroups (for instance, if the goal group was populated via stream allocation from s_mb_last_groups), then start will be >= ngroups. Does this allow allocating blocks beyond the 32-bit limit for indirect block mapped files? The commit message mentions that ext4_mb_scan_groups_linear() takes care to not select unsupported groups. However, its loop uses group = *start, and the very first iteration will call ext4_mb_scan_group() with this unsupported group because next_linear_group() is only called at the end of the iteration. After reviewing the code paths involved and considering the LLM review, I determined that this can happen when there is a file system where some files/directories are extent-mapped and others are indirect-block mapped. To address this, add a safety clamp in ext4_mb_scan_groups(). Fixes: 4865c768b563 ("ext4: always allocate blocks only from groups inode can use") Cc: Jan Kara Reviewed-by: Baokun Li Reviewed-by: Jan Kara Signed-off-by: Theodore Ts'o Link: https://patch.msgid.link/20260326045834.1175822-1-tytso@mit.edu Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/mballoc.c | 2 ++ 1 file changed, 2 insertions(+) --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1199,6 +1199,8 @@ static int ext4_mb_scan_groups(struct ex /* searching for the right group start from the goal value specified */ start = ac->ac_g_ex.fe_group; + if (start >= ngroups) + start = 0; ac->ac_prefetch_grp = start; ac->ac_prefetch_nr = 0;