From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (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 064EB8634F for ; Thu, 23 Oct 2025 00:34:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761179685; cv=none; b=g5MfElUkJFqgbiGvHmbgKWbcd80POmQopm0gwTbCqNFFwn/7aQKd9ihkha+NJuPOGbiTNDp+03JNr4Be0hprmGJs7gFoavjr3Dqpjq6caadSaYa09gTZjEmOLSnEkwEo9yU8iclLLPZDeBicZVVu7HirDyN79z/UWX9XObYZnhw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761179685; c=relaxed/simple; bh=VbP8hKIgE+Rh8j5M/iC9r6egtTdfEePGsvnfpyuKSl8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JSWHHCK2E9OovkP9pAVTMs6UWwTBj2CCzV5W57XpF70tiATT1jcCDYYwtMumUC5XAcWIqktFzqkdl/qR+5KYh8pKmqvBBA+5nTGK8eI7jvY9NwDHZjjxZz1JyhxxUruIsYVn311poPo1iWzL0FOQ5MUBMfYWxr9ZsBEWEnmkhXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=mxM4jHcV; arc=none smtp.client-ip=115.124.30.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="mxM4jHcV" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1761179673; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=qaRdQ14OHL0WfmsOQPkRYZ8UjJCfwwEcnSEpRGwSVQA=; b=mxM4jHcVCsN6+hICE4/GFX3kPk0TKfAiANV2KJTCBuZyvYjJUrPmJzKTJJ2n2rnGWanesfkXCOtlyj+56p+nc0pYKsI0wh9teso2Y0aB6VXUEQeAEtXSvODF9KcdzRWIv6iI0tsO59jKA2gj0Ir8DT2r38lAKqfwu1ldDIBbsRY= Received: from 30.221.128.75(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0WqoRGfY_1761179672 cluster:ay36) by smtp.aliyun-inc.com; Thu, 23 Oct 2025 08:34:32 +0800 Message-ID: <0573c9f8-5f72-448f-8abc-fb5b67626c9a@linux.alibaba.com> Date: Thu, 23 Oct 2025 08:34:31 +0800 Precedence: bulk X-Mailing-List: ocfs2-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC RFT PATCH] ocfs2: Invalidate inode if i_mode is zero after block read To: Ahmet Eray Karadag , mark@fasheh.com, jlbec@evilplan.org, Heming Zhao Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, david.hunter.linux@gmail.com, skhan@linuxfoundation.org, syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com, Albin Babu Varghese References: <20251022222752.46758-2-eraykrdg1@gmail.com> From: Joseph Qi In-Reply-To: <20251022222752.46758-2-eraykrdg1@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2025/10/23 06:27, Ahmet Eray Karadag wrote: > A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when > handling a corrupted inode with i_mode=0 and i_nlink=0 in memory. > > This "zombie" inode is created because ocfs2_read_locked_inode proceeds > even after ocfs2_validate_inode_block successfully validates a block > that structurally looks okay (passes checksum, signature etc.) but > contains semantically invalid data (specifically i_mode=0). The current > validation function doesn't check for i_mode being zero. > > This results in an in-memory inode with i_mode=0 being added to the VFS > cache, which later triggers the panic during unlink. > > Prevent this by adding an explicit check for i_mode == 0 within > ocfs2_validate_inode_block. If i_mode is zero, return -EFSCORRUPTED to signal > corruption. This causes the caller (ocfs2_read_locked_inode) to invoke > make_bad_inode(), correctly preventing the zombie inode from entering > the cache. > > --- > [RFC]: > The current fix handles i_mode=0 corruption detected during inode read > by returning -EFSCORRUPTED from ocfs2_validate_inode_block, which leads to > make_bad_inode() being called, preventing the corrupted inode from > entering the cache. This approach avoids immediately forcing the entire > filesystem read-only, assuming the corruption might be localized to > this inode. > > Is this less aggressive error handling strategy appropriate for i_mode=0 > corruption? Or is this condition considered severe enough that we *should* > explicitly call ocfs2_error() within the validation function to guarantee > the filesystem is marked read-only immediately upon detection? > Feedback and testing on the correct severity assessment and error > handling for this type of corruption would be appreciated. > --- > > Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com > Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b > Co-developed-by: Albin Babu Varghese > Signed-off-by: Albin Babu Varghese > Signed-off-by: Ahmet Eray Karadag > --- > fs/ocfs2/inode.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c > index 14bf440ea4df..d4142ff9ce65 100644 > --- a/fs/ocfs2/inode.c > +++ b/fs/ocfs2/inode.c > @@ -1456,6 +1456,12 @@ int ocfs2_validate_inode_block(struct super_block *sb, > goto bail; > } > > + if (unlikely(le16_to_cpu(di->i_mode) == 0)) { It seems the buggy image is carefully crafted so that it can pass the OCFS2_VALID_FL check. Checking i_mode here looks wried. Could we check i_links_count instead? Thanks, Joseph > + mlog(ML_ERROR, "Invalid dinode #%llu: i_mode is zero!\n", > + (unsigned long long)bh->b_blocknr); > + rc = -EFSCORRUPTED; > + goto bail; > + } > /* > * Errors after here are fatal. > */