From nobody Wed Dec 17 12:25:26 2025 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 39AD4C4167B for ; Mon, 27 Nov 2023 06:29:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229565AbjK0G3S (ORCPT ); Mon, 27 Nov 2023 01:29:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229509AbjK0G3Q (ORCPT ); Mon, 27 Nov 2023 01:29:16 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89F63CE; Sun, 26 Nov 2023 22:29:22 -0800 (PST) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Sdwdf3Q83zWhsG; Mon, 27 Nov 2023 14:28:38 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 27 Nov 2023 14:29:18 +0800 From: Baokun Li To: CC: , , , , , , , , , , Subject: [PATCH] ext4: prevent the normalized size from exceeding EXT_MAX_BLOCKS Date: Mon, 27 Nov 2023 14:33:13 +0800 Message-ID: <20231127063313.3734294-1-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" For files with logical blocks close to EXT_MAX_BLOCKS, the file size predicted in ext4_mb_normalize_request() may exceed EXT_MAX_BLOCKS. This can cause some blocks to be preallocated that will not be used. And after [Fixes], the following issue may be triggered: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D kernel BUG at fs/ext4/mballoc.c:4653! Internal error: Oops - BUG: 00000000f2000800 [#1] SMP CPU: 1 PID: 2357 Comm: xfs_io 6.7.0-rc2-00195-g0f5cc96c367f Hardware name: linux,dummy-virt (DT) pc : ext4_mb_use_inode_pa+0x148/0x208 lr : ext4_mb_use_inode_pa+0x98/0x208 Call trace: ext4_mb_use_inode_pa+0x148/0x208 ext4_mb_new_inode_pa+0x240/0x4a8 ext4_mb_use_best_found+0x1d4/0x208 ext4_mb_try_best_found+0xc8/0x110 ext4_mb_regular_allocator+0x11c/0xf48 ext4_mb_new_blocks+0x790/0xaa8 ext4_ext_map_blocks+0x7cc/0xd20 ext4_map_blocks+0x170/0x600 ext4_iomap_begin+0x1c0/0x348 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D Here is a calculation when adjusting ac_b_ex in ext4_mb_new_inode_pa(): ex.fe_logical =3D orig_goal_end - EXT4_C2B(sbi, ex.fe_len); if (ac->ac_o_ex.fe_logical >=3D ex.fe_logical) goto adjust_bex; The problem is that when orig_goal_end is subtracted from ac_b_ex.fe_len it is still greater than EXT_MAX_BLOCKS, which causes ex.fe_logical to overflow to a very small value, which ultimately triggers a BUG_ON in ext4_mb_new_inode_pa() because pa->pa_free < len. The last logical block of an actual write request does not exceed EXT_MAX_BLOCKS, so in ext4_mb_normalize_request() also avoids normalizing the last logical block to exceed EXT_MAX_BLOCKS to avoid the above issue. The test case in [Link] can reproduce the above issue with 64k block size. Link: https://patchwork.kernel.org/project/fstests/list/?series=3D804003 Cc: stable@kernel.org # 6.4 Fixes: 93cdf49f6eca ("ext4: Fix best extent lstart adjustment logic in ext4= _mb_new_inode_pa()") Signed-off-by: Baokun Li Reviewed-by: Jan Kara --- fs/ext4/mballoc.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 454d5612641e..d72b5e3c92ec 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4478,6 +4478,10 @@ ext4_mb_normalize_request(struct ext4_allocation_con= text *ac, start =3D max(start, rounddown(ac->ac_o_ex.fe_logical, (ext4_lblk_t)EXT4_BLOCKS_PER_GROUP(ac->ac_sb))); =20 + /* avoid unnecessary preallocation that may trigger assertions */ + if (start + size > EXT_MAX_BLOCKS) + size =3D EXT_MAX_BLOCKS - start; + /* don't cover already allocated blocks in selected range */ if (ar->pleft && start <=3D ar->lleft) { size -=3D ar->lleft + 1 - start; --=20 2.31.1