From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 229A63126AD for ; Wed, 15 Oct 2025 06:42:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=140.211.166.138 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760510524; cv=none; b=rRgKNQB2nNv7dd78eKTO2vE9MniRsfg23rcVJ4fshbkp/lPA5eEfzq2Hb4/Jrf+yjnskfCNkazytQT/ULpPtChxjWS9WXOMK6BJppeOSZC8k3v9in2YEQOPBPzR6vjNKmr1n1JVdM6h+HNw6JYOi9MW9cqs8TUoRK9s7PrY7yi8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760510524; c=relaxed/simple; bh=7ueWLGthCRnKiKyK3au2L4WjMFYE/UlGA7PZ+YmJV/s=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=Gzx0uknx/8V8PkkQOs8KyNDLU/TD4jpYa9t7ThCXkqkGfYMQ8iS4gMXyFHWiN+mRXG+7zqQ0/KAT3W19UQenKVrnkB5NCfpy6cEK98sX3oeEw8rqdaP22yRZn1uZ6aKS2bAXqpe+cBjSX+6E0D1nuyEq1GOuYWo+d+wwG3zp4Lw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Yv8q55Xv; arc=none smtp.client-ip=140.211.166.138 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Yv8q55Xv" Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id C24A683EE7 for ; Wed, 15 Oct 2025 06:42:02 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org X-Spam-Flag: NO X-Spam-Score: -5.792 X-Spam-Level: Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id fd4tVtn2goYt for ; Wed, 15 Oct 2025 06:42:02 +0000 (UTC) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=172.105.4.254; helo=tor.source.kernel.org; envelope-from=chao@kernel.org; receiver= DMARC-Filter: OpenDMARC Filter v1.4.2 smtp1.osuosl.org B7F0083ED5 Authentication-Results: smtp1.osuosl.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org B7F0083ED5 Authentication-Results: smtp1.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=Yv8q55Xv Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by smtp1.osuosl.org (Postfix) with ESMTPS id B7F0083ED5 for ; Wed, 15 Oct 2025 06:42:01 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id AEF8E6298A; Wed, 15 Oct 2025 06:41:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A379BC4CEF8; Wed, 15 Oct 2025 06:41:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760510519; bh=7ueWLGthCRnKiKyK3au2L4WjMFYE/UlGA7PZ+YmJV/s=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=Yv8q55XvvArrOpwOBYMqk5hpoKouIC/IPOpP3MD52LD0MW9IUufWtKcqXjTGU8/Bs alIlAbR6oQp0MSVgD0F29NogUp8RgWz8tKJwTVj24DZkQ9myEY1/W0Z9TEyK6qD0V1 OPLEgM8EwmHTftNdefy5SISCqRlDub1MQZKS59Usv8BozeZgG3JiT6HTBagw6rBSvT da8gWj4aiVzxdcFwFT55fjvKDQ6PwPL7tNEQJ0YPUcmsmz8RGuIY2JoMsv8/1TI6DA 3z7rt+05fI0DiqPgrtPbLq5AW6ZMcJHg9osnOEqSZYvDpbzExJiCUJuOUb0srFVpLr 1zfTILTjGWpAQ== Message-ID: <235adbae-cc45-4b84-b712-1ba9e5a48dce@kernel.org> Date: Wed, 15 Oct 2025 14:41:53 +0800 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, linux-kernel-mentees@lists.linuxfoundation.org, khalid@kernel.org, syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com Subject: Re: [PATCH] f2fs: Perform sanity check before unlinking directory inode To: "Nikola Z. Ivanov" References: <20251003134731.470392-1-zlatistiv@gmail.com> <839306c1-5f7a-4e89-b2cf-7534d279a03c@kernel.org> <9d0fef9d-4093-4a80-af3f-6dc45ffe886c@kernel.org> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/14/25 20:17, Nikola Z. Ivanov wrote: > On Mon, Oct 13, 2025 at 08:53:04PM +0800, Chao Yu wrote: >> On 10/13/25 05:19, Nikola Z. Ivanov wrote: >>> On Thu, Oct 09, 2025 at 10:54:40AM +0800, Chao Yu wrote: >>>> On 10/3/2025 9:47 PM, Nikola Z. Ivanov wrote: >>>>> Current i_nlink corruption check does not take into account >>>>> directory inodes which have one additional i_nlink for their "." entry. >>>>> >>>>> Add additional check and a common corruption path. >>>>> >>>>> Reported-by: syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com >>>>> Closes: https://syzkaller.appspot.com/bug?extid=c07d47c7bc68f47b9083 >>>>> Fixes: 81edb983b3f5 ("f2fs: add check for deleted inode") >>>>> Signed-off-by: Nikola Z. Ivanov >>>>> --- >>>>> fs/f2fs/namei.c | 28 ++++++++++++++++++++-------- >>>>> 1 file changed, 20 insertions(+), 8 deletions(-) >>>>> >>>>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c >>>>> index b882771e4699..68b33e8089b0 100644 >>>>> --- a/fs/f2fs/namei.c >>>>> +++ b/fs/f2fs/namei.c >>>>> @@ -502,12 +502,14 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry, >>>>> goto out; >>>>> } >>>>> - if (inode->i_nlink == 0) { >>>>> + if (unlikely(inode->i_nlink == 0)) { >>>>> f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has zero i_nlink", >>>>> __func__, inode->i_ino); >>>>> - err = -EFSCORRUPTED; >>>>> - set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>> - goto out_iput; >>>>> + goto corrupted; >>>>> + } else if (unlikely(S_ISDIR(inode->i_mode) && inode->i_nlink == 1)) { >>>>> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode (ino=%lx) has a single i_nlink", >>>>> + __func__, inode->i_ino); >>>>> + goto corrupted; >>>> >>>> Can we detect such corruption in sanity_check_inode() as well? So that if >>>> f2fs internal flow calls f2fs_iget() on corrupted inode, we can set SBI_NEED_FSCK >>>> flag and then triggering fsck repairment later. >>>> >>>> Thanks, >>>> >>>>> } >>>>> if (IS_ENCRYPTED(dir) && >>>>> @@ -533,6 +535,9 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry, >>>>> trace_f2fs_lookup_end(dir, !IS_ERR_OR_NULL(new) ? new : dentry, >>>>> ino, IS_ERR(new) ? PTR_ERR(new) : err); >>>>> return new; >>>>> +corrupted: >>>>> + err = -EFSCORRUPTED; >>>>> + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>> out_iput: >>>>> iput(inode); >>>>> out: >>>>> @@ -572,10 +577,11 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry) >>>>> if (unlikely(inode->i_nlink == 0)) { >>>>> f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has zero i_nlink", >>>>> __func__, inode->i_ino); >>>>> - err = -EFSCORRUPTED; >>>>> - set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>> - f2fs_folio_put(folio, false); >>>>> - goto fail; >>>>> + goto corrupted; >>>>> + } else if (unlikely(S_ISDIR(inode->i_mode) && inode->i_nlink == 1)) { >>>>> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode (ino=%lx) has a single i_nlink", >>>>> + __func__, inode->i_ino); >>>>> + goto corrupted; >>>>> } >>>>> f2fs_balance_fs(sbi, true); >>>>> @@ -601,6 +607,12 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry) >>>>> if (IS_DIRSYNC(dir)) >>>>> f2fs_sync_fs(sbi->sb, 1); >>>>> + >>>>> + goto fail; >>>>> +corrupted: >>>>> + err = -EFSCORRUPTED; >>>>> + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>> + f2fs_folio_put(folio, false); >>>>> fail: >>>>> trace_f2fs_unlink_exit(inode, err); >>>>> return err; >>>> >>> >>> Hi Chao, >>> >>> Thank you for the suggestion. >>> I will add this to sanity_check_inode and remove it >>> from f2fs_lookup as it becomes redundant since f2fs_lookup >>> obtains the inode through f2fs_iget. For f2fs_unlink I will >>> move the i_nlink == 1 check to f2fs_rmdir. >> >> Hi Nikola, >> >> I meant we can move the i_nlink == 1 check from both f2fs_lookup() and >> f2fs_unlink() to sanity_check_inode(), because before we create in-memory >> inode, we will always call sanity_check_inode(). >> >> Let me know if you have other concerns. >> >> Thanks, >> > > The issue here is that sanity_check_inode will be called only when > we initially read the inode off disk, not when it's already in the cache > > The syzkaller repro does something like this: > Creates a directory structure /dir1/dir2 where dir1 has > i_nlink == 2, which is one less than it should. It then does > rmdir(/dir1/dir2) followed by rmdir(/dir1) which leads to the warning. Oh, I missed this case. > > In such case what would you say should happen, should the second rmdir > fail and report the corruption, or do we close our eyes and just drop > i_nlink to 0 and possibly log a message that something isn't quite right? I agreed that we should keep i_nlink == 1 check in f2fs_unlink(). Thanks, > > Thank you, > >>> >>> I will send v2 as soon as I do some more testing. >>