From nobody Sat Feb 7 20:44:21 2026 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 C03BDC7EE23 for ; Tue, 23 May 2023 06:18:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231269AbjEWGSX (ORCPT ); Tue, 23 May 2023 02:18:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233664AbjEWGSL (ORCPT ); Tue, 23 May 2023 02:18:11 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54663E7B for ; Mon, 22 May 2023 23:17:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 08F8762F6D for ; Tue, 23 May 2023 06:17:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06CD8C433EF; Tue, 23 May 2023 06:17:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684822650; bh=38y7NLa808DqjIF9OA8vbOvXbxxZjQco8ZcDj1mr0Lc=; h=From:To:Cc:Subject:Date:From; b=MZNr4UghA8rCfBeNk9r38fP4XHOsdRFRLn4O6Da8m0Y5SiWzmDiio/GdoT3C2OmZu j+5ljBGJZZHCU+/hYsjiCnakTkOEcOuh4RgeKVtKhE/KKeLAG7ueMjCkEhuuI6CsDA qNqvEYJVnzOCfhlyhkj659cQ8BbVLHkOezpknZTKWZbxWunJTzJRPH3biGsRY667lJ aKMZR6/mGoIvMy1gQpfspZDSn4iC0FJjWL66Zopaz+vBGCZvhz9hFTul1AI8CelUN0 +cxmZO8OXLQrtvxAS7cxF/vetiOw5zkhVO/0a+MrHuo+k/f8xNJ8dh9qsUx84oFqB7 eMGBmdw72c9Og== From: Chao Yu To: jaegeuk@kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Chao Yu , butt3rflyh4ck Subject: [PATCH v2] f2fs: fix to avoid NULL pointer dereference f2fs_write_end_io() Date: Tue, 23 May 2023 14:17:25 +0800 Message-Id: <20230523061725.650692-1-chao@kernel.org> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" butt3rflyh4ck reports a bug as below: When a thread always calls F2FS_IOC_RESIZE_FS to resize fs, if resize fs is failed, f2fs kernel thread would invoke callback function to update f2fs io info, it would call f2fs_write_end_io and may trigger null-ptr-deref in NODE_MAPPING. general protection fault, probably for non-canonical address KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] RIP: 0010:NODE_MAPPING fs/f2fs/f2fs.h:1972 [inline] RIP: 0010:f2fs_write_end_io+0x727/0x1050 fs/f2fs/data.c:370 bio_endio+0x5af/0x6c0 block/bio.c:1608 req_bio_endio block/blk-mq.c:761 [inline] blk_update_request+0x5cc/0x1690 block/blk-mq.c:906 blk_mq_end_request+0x59/0x4c0 block/blk-mq.c:1023 lo_complete_rq+0x1c6/0x280 drivers/block/loop.c:370 blk_complete_reqs+0xad/0xe0 block/blk-mq.c:1101 __do_softirq+0x1d4/0x8ef kernel/softirq.c:571 run_ksoftirqd kernel/softirq.c:939 [inline] run_ksoftirqd+0x31/0x60 kernel/softirq.c:931 smpboot_thread_fn+0x659/0x9e0 kernel/smpboot.c:164 kthread+0x33e/0x440 kernel/kthread.c:379 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308 The root cause is below race case can cause leaving dirty metadata in f2fs after filesystem is remount as ro: Thread A Thread B - f2fs_ioc_resize_fs - f2fs_readonly --- return false - f2fs_resize_fs - f2fs_remount - write_checkpoint - set f2fs as ro - free_segment_range - update meta_inode's data Then, if f2fs_put_super() fails to write_checkpoint due to readonly status, and meta_inode's dirty data will be writebacked after node_inode is put, finally, f2fs_write_end_io will access NULL pointer on sbi->node_inode. Thread A IRQ context - f2fs_put_super - write_checkpoint fails - iput(node_inode) - node_inode =3D NULL - iput(meta_inode) - write_inode_now - f2fs_write_meta_page - f2fs_write_end_io - NODE_MAPPING(sbi) : access NULL pointer on node_inode Fixes: b4b10061ef98 ("f2fs: refactor resize_fs to avoid meta updates in pro= gress") Reported-by: butt3rflyh4ck Closes: https://lore.kernel.org/r/1684480657-2375-1-git-send-email-yangtiez= hu@loongson.cn Tested-by: butt3rflyh4ck Signed-off-by: Chao Yu --- v2: - update commit message a bit - add Tested-by tag fs/f2fs/f2fs.h | 2 +- fs/f2fs/file.c | 2 +- fs/f2fs/gc.c | 21 ++++++++++++++++++--- 3 files changed, 20 insertions(+), 5 deletions(-) diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index c604523a22c2..e28cbb89b063 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -3843,7 +3843,7 @@ void f2fs_stop_gc_thread(struct f2fs_sb_info *sbi); block_t f2fs_start_bidx_of_node(unsigned int node_ofs, struct inode *inode= ); int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control); void f2fs_build_gc_manager(struct f2fs_sb_info *sbi); -int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count); +int f2fs_resize_fs(struct file *filp, __u64 block_count); int __init f2fs_create_garbage_collection_cache(void); void f2fs_destroy_garbage_collection_cache(void); /* victim selection function for cleaning and SSR */ diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 78aa8cff4b41..015ed274dc31 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -3279,7 +3279,7 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsi= gned long arg) sizeof(block_count))) return -EFAULT; =20 - return f2fs_resize_fs(sbi, block_count); + return f2fs_resize_fs(filp, block_count); } =20 static int f2fs_ioc_enable_verity(struct file *filp, unsigned long arg) diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 35b95b3d57ef..8cbe4839f640 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -2195,8 +2195,9 @@ static void update_fs_metadata(struct f2fs_sb_info *s= bi, int secs) } } =20 -int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count) +int f2fs_resize_fs(struct file *filp, __u64 block_count) { + struct f2fs_sb_info *sbi =3D F2FS_I_SB(file_inode(filp)); __u64 old_block_count, shrunk_blocks; struct cp_control cpc =3D { CP_RESIZE, 0, 0, 0 }; unsigned int secs; @@ -2234,12 +2235,18 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 = block_count) return -EINVAL; } =20 + err =3D mnt_want_write_file(filp); + if (err) + return err; + shrunk_blocks =3D old_block_count - block_count; secs =3D div_u64(shrunk_blocks, BLKS_PER_SEC(sbi)); =20 /* stop other GC */ - if (!f2fs_down_write_trylock(&sbi->gc_lock)) - return -EAGAIN; + if (!f2fs_down_write_trylock(&sbi->gc_lock)) { + err =3D -EAGAIN; + goto out_drop_write; + } =20 /* stop CP to protect MAIN_SEC in free_segment_range */ f2fs_lock_op(sbi); @@ -2259,10 +2266,18 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 = block_count) out_unlock: f2fs_unlock_op(sbi); f2fs_up_write(&sbi->gc_lock); +out_drop_write: + mnt_drop_write_file(filp); if (err) return err; =20 freeze_super(sbi->sb); + + if (f2fs_readonly(sbi->sb)) { + thaw_super(sbi->sb); + return -EROFS; + } + f2fs_down_write(&sbi->gc_lock); f2fs_down_write(&sbi->cp_global_sem); =20 --=20 2.40.1