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 E9CA12C0282 for ; Mon, 3 Nov 2025 08:12:19 +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=1762157540; cv=none; b=AVwOw1Sc+BJhN+96Wf1vOQqcctpDv3ScvKbwOmexeP1Zwdr43cjM1dq+UvX9htGPSA2hA8nwACUpMmXG7tntk2EQu3OnBaC8Ts9riWYcnB5auF0If/hlmA1RdLFDKtjk0tuIEUcX9Dz0wOZzYR1pfIrayJ6Xm9hNKiKUf5m5iQo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762157540; c=relaxed/simple; bh=IvpnIGpW5pDCkLQfXgWwGHkEHfCk7MiqPLCNiRLC+WQ=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=bidm4QE4qcH+WHXSdVyfAJVmVY2r/MNB7bD1UWuvs269HWW1RvXCHsgFYJG9/1/uyPrcOpMn5Q7JG8rt12IgsYrBgzUvMWnxD1PbawPd0Ly5Se6v34yT40BkT8k4fM3U8XCshtpquYDPDZDgsFVdhhbQoTX5SnNeXmMMpZnwXII= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=S0YNXVS0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="S0YNXVS0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68D6AC4CEE7; Mon, 3 Nov 2025 08:12:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762157539; bh=IvpnIGpW5pDCkLQfXgWwGHkEHfCk7MiqPLCNiRLC+WQ=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=S0YNXVS0yAj8eMy8n4ZhbtQ9hC9T7Mf54lpwHTVpoKAAqh3V3nd+ZzZVWHv1SV+W5 UAd3gtBHUvErsl25wSglSV94+e8eDBDB8+xMxyHLV58f0Sqe6lPn/TWLtxh6scepw4 q1spY+AuYY/hk7wOUS7giLwwNUxKshkly3d98vZcRt5zCD8YKe0Uuttbl/D5MsOzbi m7k5AUlzhk2nB/mr+GfQBTZnFtjo5imn3No8h0N+RqcIbXSniKdUZO5aitu2TIC4Pn 8uCvFmJpzDoQRIseKnwWF1P6pLD5ClaNqTQC1KpNUhsTxWbg3yaBpYQf1kguBZhJa1 7oUS76waCD/vQ== Message-ID: <1f519357-a489-41fe-8159-a8e319aedd17@kernel.org> Date: Mon, 3 Nov 2025 16:12:15 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org 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 v2 2/2] f2fs: Add sanity checks before unlinking and loading inodes To: "Nikola Z. Ivanov" References: <55522ef8f3424e563ff18a720c709dcb065091af.1761993022.git.zlatistiv@gmail.com> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/3/25 15:55, Nikola Z. Ivanov wrote: > On Mon, Nov 03, 2025 at 10:35:17AM +0800, Chao Yu wrote: >> On 11/1/25 20:56, Nikola Z. Ivanov wrote: >>> Add check for inode->i_nlink == 1 for directories during unlink, >>> as their value is decremented twice, which can trigger a warning in >>> drop_nlink. In such case mark the filesystem as corrupted and return >>> from the function call with the relevant failure return value. >>> >>> Additionally add the 2 checks for i_nlink == 0 and i_nlink == 1 in >>> sanity_check_inode in order to detect on-disk corruption early. >>> >>> Reported-by: syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com >>> Closes: https://syzkaller.appspot.com/bug?extid=c07d47c7bc68f47b9083 >>> Tested-by: syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com >>> Signed-off-by: Nikola Z. Ivanov >>> --- >>> fs/f2fs/inode.c | 10 ++++++++++ >>> fs/f2fs/namei.c | 15 +++++++++++---- >>> 2 files changed, 21 insertions(+), 4 deletions(-) >>> >>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c >>> index 8c4eafe9ffac..089cbf3646f0 100644 >>> --- a/fs/f2fs/inode.c >>> +++ b/fs/f2fs/inode.c >>> @@ -294,6 +294,16 @@ static bool sanity_check_inode(struct inode *inode, struct folio *node_folio) >>> return false; >>> } >>> >>> + if (unlikely(inode->i_nlink == 0)) { >> >> This is a possible case, as an orphan inode may exist in filesystem after sudden >> power-cut. >> >> Thanks, >> > > Hi Chao, > > Do you suggest that it should not be wrapped in unlikely()? Nikola, No, I think we should not add this sanity check "inode->i_nlink == 0" into sanity_check_inode(), as for an orphan inode, its i_nlink is zero. We expect to get the inode w/o failure in recover_orphan_inode(). > > I also now realise that I intended to wrap the "else if" case > as well but I've missed it in the final patch. Looks fine to add unlike for the "dir->i_nlink == 1" case. Thanks, > > Should I resend the patch with both cases wrapped in "unlikely()" > or would you suggest otherwise? > > >>> + f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has zero i_nlink", >>> + __func__, inode->i_ino); >>> + return false; >>> + } else if (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); >>> + return false; >>> + } >>> + >>> if (f2fs_has_extra_attr(inode)) { >>> if (!f2fs_sb_has_extra_attr(sbi)) { >>> f2fs_warn(sbi, "%s: inode (ino=%lx) is with extra_attr, but extra_attr feature is off", >>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c >>> index 40cf80fd9d9a..d13077bad482 100644 >>> --- a/fs/f2fs/namei.c >>> +++ b/fs/f2fs/namei.c >>> @@ -572,10 +572,11 @@ 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 out; >>> + goto corrupted; >>> + } else if (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 +602,12 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry) >>> >>> if (IS_DIRSYNC(dir)) >>> f2fs_sync_fs(sbi->sb, 1); >>> + >>> + goto out; >>> +corrupted: >>> + err = -EFSCORRUPTED; >>> + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>> + f2fs_folio_put(folio, false); >>> out: >>> trace_f2fs_unlink_exit(inode, err); >>> return err; >>