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 4CC8D1E5B97 for ; Wed, 4 Jun 2025 09:48:51 +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=1749030532; cv=none; b=P0kMv1jERQutuKIjZ9Xap6aiqGGl0ZipWfAlSMqT6E8dZVRed8dhB/M0xWHtB1rbDxTVjhPOOnK9BnsEyjIjtsdh75gGgVbkCye0wy1mbhoEDv8yrla/6BqXaT15v7DIteEjGtoVqqbczeLZQu/g6QZBoyOaRDdqXqxC7NY1624= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749030532; c=relaxed/simple; bh=pbdV4FPg+q7X6VNKgCyiuIlkd0/NfsNnQ/IoEFmOi0Q=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=X/IiSlbyLSAOWRQcxxCCfBz5gGCPZ5hyqlG3RQwwH6JH6RElGkw20JfVfJvUYChe+A9nattZRv2+mL0pD5m0U7qCxwr7QPxF3vz8skBp6Z8idNoYLyRSAryknadcnsSuQj2oZmRoPfBsH+HEyhh0fUxyL8kbKKomgZJ5+cGJMMM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=LF7iY5xA; 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="LF7iY5xA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8741C4CEE7; Wed, 4 Jun 2025 09:48:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749030531; bh=pbdV4FPg+q7X6VNKgCyiuIlkd0/NfsNnQ/IoEFmOi0Q=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=LF7iY5xADR0LXMGkmm3+bM5eMGvuyWceDXQquWYHJu8o1DPGweDZUlbzSun2oxC3O i3kw8nB+PYnttftlV0vYg5XjKjdBopEPmcgtYqBZcBo+Nz/qSn6gsmUaz5n/PzrGhA JyMCaTySGc34cBPHkY6frvjDwcqawYDJuPVvJlAoGAEZVYonc7rlBOeHBpRudP1AgP Tzl58nSAPGh+/Q2S7eRAKjKZqtjlt1+lXQKHT9ZkktGx8M0DUapK8BLy5djzbfq1qr Y9a2u1fZrCbtM3LhFOva3vRDZTAZsU+qY48KDXKVAovDq/4h+Xa9EkI19YznbbyfoJ wA+jhVm3U4duQ== Message-ID: <061c94ab-ff57-42e3-ad7c-592dfb2a822e@kernel.org> Date: Wed, 4 Jun 2025 17:48:47 +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, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, niuzhiguo84@gmail.com, ke.wang@unisoc.com, Hao_hao.Wang@unisoc.com, baocong.liu@unisoc.com Subject: Re: [PATCH] f2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic To: Zhiguo Niu , jaegeuk@kernel.org References: <1749016492-31835-1-git-send-email-zhiguo.niu@unisoc.com> Content-Language: en-US From: Chao Yu In-Reply-To: <1749016492-31835-1-git-send-email-zhiguo.niu@unisoc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/4/25 13:54, Zhiguo Niu wrote: > The decompress_io_ctx may be released asynchronously after > I/O completion. If this file is deleted immediately after read, > and the kworker of processing post_read_wq has not been executed yet > due to high workloads, It is possible that the inode(f2fs_inode_info) > is evicted and freed before it is used f2fs_free_dic. > > The UAF case as below: > Thread A Thread B > - f2fs_decompress_end_io > - f2fs_put_dic > - queue_work > add free_dic work to post_read_wq > - do_unlink > - iput > - evict > - call_rcu > This file is deleted after read. > > Thread C kworker to process post_read_wq > - rcu_do_batch > - f2fs_free_inode > - kmem_cache_free > inode is freed by rcu > - process_scheduled_works > - f2fs_late_free_dic > - f2fs_free_dic > - f2fs_release_decomp_mem > read (dic->inode)->i_compress_algorithm > > This patch increase inode->i_count before f2fs_free_dic and decrease it > after free the dic. > > Cc: Daeho Jeong > Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq") > Signed-off-by: Zhiguo Niu > Signed-off-by: Baocong Liu > --- > fs/f2fs/compress.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c > index b3c1df9..6b3b3a7 100644 > --- a/fs/f2fs/compress.c > +++ b/fs/f2fs/compress.c > @@ -1687,7 +1687,7 @@ static void f2fs_release_decomp_mem(struct decompress_io_ctx *dic, > } > > static void f2fs_free_dic(struct decompress_io_ctx *dic, > - bool bypass_destroy_callback); > + bool bypass_destroy_callback, bool late_free); > > struct decompress_io_ctx *f2fs_alloc_dic(struct compress_ctx *cc) > { > @@ -1743,12 +1743,12 @@ struct decompress_io_ctx *f2fs_alloc_dic(struct compress_ctx *cc) > return dic; > > out_free: > - f2fs_free_dic(dic, true); > + f2fs_free_dic(dic, true, false); > return ERR_PTR(ret); > } > > static void f2fs_free_dic(struct decompress_io_ctx *dic, > - bool bypass_destroy_callback) > + bool bypass_destroy_callback, bool late_free) > { > int i; > > @@ -1775,6 +1775,11 @@ static void f2fs_free_dic(struct decompress_io_ctx *dic, > } > > page_array_free(dic->inode, dic->rpages, dic->nr_rpages); > + if (late_free) { > + spin_lock(&dic->inode->i_lock); > + atomic_dec(&dic->inode->i_count); > + spin_unlock(&dic->inode->i_lock); If it is the last one release i_count, it needs to call iput_final to evict inode like what iput did, so we'd better to call iput() here? > + } > kmem_cache_free(dic_entry_slab, dic); > } > > @@ -1783,16 +1788,20 @@ static void f2fs_late_free_dic(struct work_struct *work) > struct decompress_io_ctx *dic = > container_of(work, struct decompress_io_ctx, free_work); > > - f2fs_free_dic(dic, false); > + f2fs_free_dic(dic, false, true); > } > > static void f2fs_put_dic(struct decompress_io_ctx *dic, bool in_task) > { > if (refcount_dec_and_test(&dic->refcnt)) { > if (in_task) { > - f2fs_free_dic(dic, false); > + f2fs_free_dic(dic, false, false); > } else { > INIT_WORK(&dic->free_work, f2fs_late_free_dic); > + /* to avoid inode is evicted simultaneously */ > + spin_lock(&dic->inode->i_lock); > + atomic_inc(&dic->inode->i_count); > + spin_unlock(&dic->inode->i_lock); iget()? BTW, can we store i_compress_algorithm in dic to avoid inode access? Thanks, > queue_work(F2FS_I_SB(dic->inode)->post_read_wq, > &dic->free_work); > }