From patchwork Tue Nov 24 02:20:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: ethanwu X-Patchwork-Id: 11926965 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34744C2D0E4 for ; Tue, 24 Nov 2020 02:26:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B908420719 for ; Tue, 24 Nov 2020 02:26:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=synology.com header.i=@synology.com header.b="AUdO9BeK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728069AbgKXC0f (ORCPT ); Mon, 23 Nov 2020 21:26:35 -0500 Received: from mail.synology.com ([211.23.38.101]:47832 "EHLO synology.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726770AbgKXC0f (ORCPT ); Mon, 23 Nov 2020 21:26:35 -0500 X-Greylist: delayed 354 seconds by postgrey-1.27 at vger.kernel.org; Mon, 23 Nov 2020 21:26:33 EST From: ethanwu DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=synology.com; s=123; t=1606184438; bh=/jjP/xSHgUrO7qByK4NKdNyklqGo10amPe7sNAGlhuE=; h=From:To:Cc:Subject:Date; b=AUdO9BeKg8FRsqwjnPhBNJTlp5l3SvRFUP9/ePj6tawO7ioSixlUPLY7eBjPImN8n CmboyJb4Y25oao7+nbsdHawlpHm37aT9Qonp03MSGDO6LaCPuYLg5awsV2d8tdPhlu DKB999jWupP2/WuOCFjS7rUt1j7GyDRsHIboJ5Aw= To: linux-btrfs@vger.kernel.org Cc: ethanwu Subject: [PATCH 1/1] Btrfs: correctly calculate item size used when item key collision happends Date: Tue, 24 Nov 2020 10:20:36 +0800 Message-Id: <20201124022036.2840981-1-ethanwu@synology.com> MIME-Version: 1.0 X-Synology-MCP-Status: no X-Synology-Spam-Flag: no X-Synology-Spam-Status: score=0, required 6, WHITELIST_FROM_ADDRESS 0 X-Synology-Virus-Status: no Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Item key collision is allowed for some item types, like dir item and inode refs, but the overall item size is limited by the leafsize. item size(ins_len) passed from btrfs_insert_empty_items to btrfs_search_slot already contains size of btrfs_item. When btrfs_search_slot reaches leaf, we'll see if we need to split leaf. The check incorrectly reports that split leaf is required, because it treats the space required by the newly inserted item as btrfs_item + item data. But in item key collision case, only item data is actually needed, the newly inserted item could merge into the existing one. No new btrfs_item will be inserted. And split_leaf return -EOVERFLOW from following code: if (extend && data_size + btrfs_item_size_nr(l, slot) + sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(fs_info)) return -EOVERFLOW; In most cases, when callers receive -EOVERFLOW, they either return this error or handle in different ways. For example, in normal dir item creation the userspace will get errno EOVERFLOW; in inode ref case INODE_EXTREF is used instead. However, this is not the case for rename. To avoid the unrecoverable situation in rename, btrfs_check_dir_item_collision is called in early phase of rename. In this function, when item key collision is detected leaf space is checked: data_size = sizeof(*di) + name_len; if (data_size + btrfs_item_size_nr(leaf, slot) + sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root->fs_info)) the sizeof(struct btrfs_item) + btrfs_item_size_nr(leaf, slot) here refers to existing item size, the condition here correctly calculate the needed size for collision case rather than the wrong case at above. The consequence of inconsistent condition check between btrfs_check_dir_item_collision and btrfs_search_slot when item key collision happens is that we might pass check here but fail later at btrfs_search_slot. Rename fails and volume is forced readonly [436149.586170] ------------[ cut here ]------------ [436149.586173] BTRFS: Transaction aborted (error -75) [436149.586196] WARNING: CPU: 0 PID: 16733 at fs/btrfs/inode.c:9870 btrfs_rename2+0x1938/0x1b70 [btrfs] [436149.586197] Modules linked in: btrfs zstd_compress xor raid6_pq ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs libcrc32c rpcsec_gss_krb5 coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel aes_x86_64 vmw_balloon crypto_simd cryptd glue_helper joydev input_leds intel_rapl_perf serio_raw vmw_vmci mac_hid sch_fq_codel nfsd auth_rpcgss nfs_acl lockd grace sunrpc parport_pc ppdev lp parport ip_tables x_tables autofs4 vmwgfx ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm psmouse mptspi mptscsih mptbase scsi_transport_spi ahci vmxnet3 libahci i2c_piix4 floppy pata_acpi [436149.586227] CPU: 0 PID: 16733 Comm: python Tainted: G D 4.18.0-rc5+ #1 [436149.586228] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 04/05/2016 [436149.586238] RIP: 0010:btrfs_rename2+0x1938/0x1b70 [btrfs] [436149.586238] Code: 50 f0 48 0f ba a8 10 ce 00 00 02 72 27 41 83 f8 fb 74 6f 44 89 c6 48 c7 c7 48 09 85 c0 44 89 55 80 44 89 45 98 e8 f8 5e 4c c5 <0f> 0b 44 8b 45 98 44 8b 55 80 44 89 55 80 44 89 c1 44 89 45 98 ba [436149.586254] RSP: 0018:ffffa327043a7ce0 EFLAGS: 00010286 [436149.586255] RAX: 0000000000000000 RBX: ffff8d8a17d13340 RCX: 0000000000000006 [436149.586256] RDX: 0000000000000007 RSI: 0000000000000096 RDI: ffff8d8a7fc164b0 [436149.586257] RBP: ffffa327043a7da0 R08: 0000000000000560 R09: 7265282064657472 [436149.586258] R10: 0000000000000000 R11: 6361736e61725420 R12: ffff8d8a0d4c8b08 [436149.586258] R13: ffff8d8a17d13340 R14: ffff8d8a33e0a540 R15: 00000000000001fe [436149.586260] FS: 00007fa313933740(0000) GS:ffff8d8a7fc00000(0000) knlGS:0000000000000000 [436149.586261] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [436149.586262] CR2: 000055d8d9c9a720 CR3: 000000007aae0003 CR4: 00000000003606f0 [436149.586295] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [436149.586296] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [436149.586296] Call Trace: [436149.586311] vfs_rename+0x383/0x920 [436149.586313] ? vfs_rename+0x383/0x920 [436149.586315] do_renameat2+0x4ca/0x590 [436149.586317] __x64_sys_rename+0x20/0x30 [436149.586324] do_syscall_64+0x5a/0x120 [436149.586330] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [436149.586332] RIP: 0033:0x7fa3133b1d37 [436149.586332] Code: 75 12 48 89 df e8 89 60 09 00 85 c0 0f 95 c0 0f b6 c0 f7 d8 5b c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 b8 52 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 09 f3 c3 0f 1f 80 00 00 00 00 48 8b 15 19 f1 [436149.586348] RSP: 002b:00007fffd3e43908 EFLAGS: 00000246 ORIG_RAX: 0000000000000052 [436149.586349] RAX: ffffffffffffffda RBX: 00007fa3133b1d30 RCX: 00007fa3133b1d37 [436149.586350] RDX: 000055d8da06b5e0 RSI: 000055d8da225d60 RDI: 000055d8da2c4da0 [436149.586351] RBP: 000055d8da2252f0 R08: 00007fa313782000 R09: 00000000000177e0 [436149.586351] R10: 000055d8da010680 R11: 0000000000000246 R12: 00007fa313840b00 Thanks to Hans van Kranenburg for information about crc32 hash collision tools, I was able to reproduce the dir item collision with following python script. https://github.com/wutzuchieh/misc_tools/blob/master/crc32_forge.py Run it under a btrfs volume will trigger the abort transaction. It simply creates files and rename them to forged names that leads to hash collision. There are two ways to fix this. One is to simply revert the patch "878f2d2cb355 Btrfs: fix max dir item size calculation" to make the condition consistent although that patch is correct about the size. The other way is to handle the leaf space check correctly when collision happens. I prefer the second one since it correct leaf space check in collision case. This fix needs unify the usage of ins_len in btrfs_search_slot to contain btrfs_item anyway and adjust all callers of btrfs_search_slot that intentionally pass ins_len without btrfs_item size to add size of btrfs_item from now. Signed-off-by: ethanwu --- v3: modify comment for btrfs_search_lot parameter ins_len, fix incorrect ins_len in lookup_inline_extent_backref and btrfs_csum_file_blocks fs/btrfs/ctree.c | 16 ++++++++++++++-- fs/btrfs/extent-tree.c | 8 ++++++-- 2 files changed, 20 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 32a57a70b98d..084b55d4c397 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2557,8 +2557,9 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root, * @p: Holds all btree nodes along the search path * @root: The root node of the tree * @key: The key we are looking for - * @ins_len: Indicates purpose of search, for inserts it is 1, for - * deletions it's -1. 0 for plain searches + * @ins_len: Indicates purpose of search, for inserts it is a positive + * number (size of item inserted), for deletions it's a negative number and + * 0 for plain searches, not modifying the tree. * @cow: boolean should CoW operations be performed. Must always be 1 * when modifying the tree. * @@ -2719,6 +2720,17 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, if (level == 0) { p->slots[level] = slot; + /* +  * item key collision happens. In this case, if we are allow +  * to insert the item(for example, in dir_item case, item key +  * collision is allowed), it will be merged with the original +  * item. Only the item size grows, no new btrfs item will be +  * added. Since the ins_len already accounts the size btrfs_item, +  * this value is counted twice. Duduct this value here so the +  * leaf space check will be correct. +  */ + if (ret == 0 && ins_len > 0) + ins_len -= sizeof(struct btrfs_item); if (ins_len > 0 && btrfs_leaf_free_space(b) < ins_len) { if (write_lock_level < 1) { diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index fc942759a04c..ead62b7ba954 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -830,6 +830,7 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans, unsigned long ptr; unsigned long end; int extra_size; + int ins_len; int type; int want; int ret; @@ -844,9 +845,12 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans, want = extent_ref_type(parent, owner); if (insert) { extra_size = btrfs_extent_inline_ref_size(want); + ins_len = extra_size + sizeof(struct btrfs_item); path->keep_locks = 1; - } else + } else { extra_size = -1; + ins_len = -1; + } /* * Owner is our level, so we can just add one to get the level for the @@ -858,7 +862,7 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans, } again: - ret = btrfs_search_slot(trans, root, &key, path, extra_size, 1); + ret = btrfs_search_slot(trans, root, &key, path, ins_len, 1); if (ret < 0) { err = ret; goto out;