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 877C128DF3A for ; Wed, 4 Jun 2025 11:09:22 +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=1749035362; cv=none; b=LqBsqRaho7yRz1zac0Fndj+Ik085izS6y9RkKW2CF8R1MxPkPhhadQN8szonVD3aHfIgZARQuyCGt8Xd4uo3BFpueF4I7EeKHHLgUvkhJGc4pe3FDGFZA9SmvczwZ9TgMUBIDIJZ6Jh3EeZuhi41yrInTJDPgSTEDZMm0pCYObM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749035362; c=relaxed/simple; bh=bxbzNNKPCagVAfsznDam2r9jaVbG7yC74u5DW2QcVFI=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=ViKqtbM+CU7c2d16hdIGuWDxSWWTd7TUm6wn4UGCCKJ8Ye3TArZcFtkviSI4EXZNC6jBI6PjybgMw9/WrdDUvglmnvRmUkiGLsHt+qJl9agBy1AUy8qcbCL8n2k9pwHtCdPcqUp2Kn9ntdDNpDV9koZ55T8gmzYLWfW1uNczNho= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=d76ficgW; 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="d76ficgW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE364C4CEE7; Wed, 4 Jun 2025 11:09:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749035362; bh=bxbzNNKPCagVAfsznDam2r9jaVbG7yC74u5DW2QcVFI=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=d76ficgWdxxqPKuMtBDUFhRi8MS/oyNrEUGQ34Bkafomm8+7djXA8UCvTJ2LHbod1 HIHzw2gV3/ck5nB472azG8/WGH6w4mn79IyRymk/W5YmOFWamKZLp1fihjvA1KTXYH WcwnjFrboIPtRrVJZ7TM5RRQAwDSQESgOhL82Xgkp3gRQ/ZETm4AIL+Orxhd/TPK2F l92pT2D7pErPMJ/itTOsIFInlaaE8dGa3oB8Tp/9jaOuFhyE+PovEuQfmC4SJ6DXGe s1q86KCXJgqMQ8lmbQA6muM8AkU6fcXJdnlpzJuayDFjY5MX/7wz84TETngsmLCoAW c/Kwmu4MeUTBg== Message-ID: <1791cead-c598-41dc-8c6c-811787df14b7@kernel.org> Date: Wed, 4 Jun 2025 19:09:17 +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, Zhiguo Niu , jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, 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 References: <1749016492-31835-1-git-send-email-zhiguo.niu@unisoc.com> <061c94ab-ff57-42e3-ad7c-592dfb2a822e@kernel.org> Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/4/25 18:49, Zhiguo Niu wrote: > Chao Yu 于2025年6月4日周三 17:48写道： >> >> 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? > Hi Chao, > Yes, we have also tested this method(iput/__iget), and it worked. > Just think It is simpler and easier to read to directly operate > i_count, and then free it > by relying on the memory module when i_count=0. > But It seems iput/__iget is better. >> >>> + } >>> 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? > > Also thought of this method, but it would require more changes. > dic->inode used in f2fs_free_dic are all needed to modify except > i_compress_algorithm. > such as page_array_free(dic->inode), Zhiguo, page_array_free() parses dic->inode to get sbi only, so we can pass sbi to page_array_free() directly to avoid using dic->inode. > allow_memalloc_for_decomp(F2FS_I_SB(dic->inode)). > > Do you have any other suggestions? Using iget/iput looks fine to me, please go ahead. Thanks, > thanks！ > >> >> Thanks, >> >>> queue_work(F2FS_I_SB(dic->inode)->post_read_wq, >>> &dic->free_work); >>> } >>