From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (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 5958824A0E; Mon, 20 May 2024 09:39:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716198000; cv=none; b=OP5LrXj9mvqrky6faUwaCDBAIAJWSSAhvz4Y8CPgtDdUewF0sOAuda5hEyp1vxzT7SDRbcNITrpbgsURonLKiTF+HQiPV2+9t8YvpJqDBwWlTFcyY5T1lgMDhsnmppx2Lh0fgiMLOwf5ihMpNLOc+gLA3dDZ3WE/fLma04z4958= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716198000; c=relaxed/simple; bh=47LN/nymBqehrBP24YKxxrHpwHOr2rH6/YWWUldHoas=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZLljXB6ktLIfFHAtRNXlenauCB/DVLj4HZCEB66C+Ew82akOEkRAnHDwDubVSh0sxOmK82fazt37YQnBUCcdpvvMUyj0DcVtfuCQ52IIeS/1p5gH+StB0q2sgmXFflTYwUFm7qqMZlFmnk4cmyXHmpPnxIZ0TnseU1hISjUezmc= 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=qrdlR/6H; arc=none smtp.client-ip=115.124.30.133 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="qrdlR/6H" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1716197994; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=6mPT0eGoRhA21v6AH8L2aZwWTPQ8/DIb/G4ER9YIgYQ=; b=qrdlR/6HP2mzeeJDw5ODpprr1QsuisZzJI4FSn+5XF4s8OCQopZzUv8J8aXZMT+zmPhKv9PaljwuwFQx/plmRUcKBGhIK3BDGot3aN88v4pXAvvidYPUl63GJSdtgKv7ikRfwc3QZsWZSzU+QWsBLpk937fQjweXcYwYOptOUbU= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R721e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037067110;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=14;SR=0;TI=SMTPD_---0W6qUXQb_1716197992; Received: from 30.221.148.185(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0W6qUXQb_1716197992) by smtp.aliyun-inc.com; Mon, 20 May 2024 17:39:54 +0800 Message-ID: Date: Mon, 20 May 2024 17:39:51 +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 Subject: Re: [PATCH v2 09/12] cachefiles: defer exposing anon_fd until after copy_to_user() succeeds To: libaokun@huaweicloud.com, netfs@lists.linux.dev, dhowells@redhat.com, jlayton@kernel.org Cc: hsiangkao@linux.alibaba.com, zhujia.zj@bytedance.com, linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, yangerkun@huawei.com, houtao1@huawei.com, yukuai3@huawei.com, wozizhi@huawei.com, Baokun Li References: <20240515084601.3240503-1-libaokun@huaweicloud.com> <20240515084601.3240503-10-libaokun@huaweicloud.com> Content-Language: en-US From: Jingbo Xu In-Reply-To: <20240515084601.3240503-10-libaokun@huaweicloud.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/15/24 4:45 PM, libaokun@huaweicloud.com wrote: > From: Baokun Li > > After installing the anonymous fd, we can now see it in userland and close > it. However, at this point we may not have gotten the reference count of > the cache, but we will put it during colse fd, so this may cause a cache > UAF. > > So grab the cache reference count before fd_install(). In addition, by > kernel convention, fd is taken over by the user land after fd_install(), > and the kernel should not call close_fd() after that, i.e., it should call > fd_install() after everything is ready, thus fd_install() is called after > copy_to_user() succeeds. > > Fixes: c8383054506c ("cachefiles: notify the user daemon when looking up cookie") > Suggested-by: Hou Tao > Signed-off-by: Baokun Li > --- > fs/cachefiles/ondemand.c | 53 +++++++++++++++++++++++++--------------- > 1 file changed, 33 insertions(+), 20 deletions(-) > > diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c > index d2d4e27fca6f..3a36613e00a7 100644 > --- a/fs/cachefiles/ondemand.c > +++ b/fs/cachefiles/ondemand.c > @@ -4,6 +4,11 @@ > #include > #include "internal.h" > > +struct anon_file { > + struct file *file; > + int fd; > +}; > + > static inline void cachefiles_req_put(struct cachefiles_req *req) > { > if (refcount_dec_and_test(&req->ref)) > @@ -263,14 +268,14 @@ int cachefiles_ondemand_restore(struct cachefiles_cache *cache, char *args) > return 0; > } > > -static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) > +static int cachefiles_ondemand_get_fd(struct cachefiles_req *req, > + struct anon_file *anon_file) How about: int cachefiles_ondemand_get_fd(struct cachefiles_req *req, int *fd, struct file *file) ? It isn't worth introducing a new structure as it is used only for parameter passing. > { > struct cachefiles_object *object; > struct cachefiles_cache *cache; > struct cachefiles_open *load; > - struct file *file; > u32 object_id; > - int ret, fd; > + int ret; > > object = cachefiles_grab_object(req->object, > cachefiles_obj_get_ondemand_fd); > @@ -282,16 +287,16 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) > if (ret < 0) > goto err; > > - fd = get_unused_fd_flags(O_WRONLY); > - if (fd < 0) { > - ret = fd; > + anon_file->fd = get_unused_fd_flags(O_WRONLY); > + if (anon_file->fd < 0) { > + ret = anon_file->fd; > goto err_free_id; > } > > - file = anon_inode_getfile("[cachefiles]", &cachefiles_ondemand_fd_fops, > - object, O_WRONLY); > - if (IS_ERR(file)) { > - ret = PTR_ERR(file); > + anon_file->file = anon_inode_getfile("[cachefiles]", > + &cachefiles_ondemand_fd_fops, object, O_WRONLY); > + if (IS_ERR(anon_file->file)) { > + ret = PTR_ERR(anon_file->file); > goto err_put_fd; > } > > @@ -299,16 +304,15 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) > if (object->ondemand->ondemand_id > 0) { > spin_unlock(&object->ondemand->lock); > /* Pair with check in cachefiles_ondemand_fd_release(). */ > - file->private_data = NULL; > + anon_file->file->private_data = NULL; > ret = -EEXIST; > goto err_put_file; > } > > - file->f_mode |= FMODE_PWRITE | FMODE_LSEEK; > - fd_install(fd, file); > + anon_file->file->f_mode |= FMODE_PWRITE | FMODE_LSEEK; > > load = (void *)req->msg.data; > - load->fd = fd; > + load->fd = anon_file->fd; > object->ondemand->ondemand_id = object_id; > spin_unlock(&object->ondemand->lock); > > @@ -317,9 +321,11 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) > return 0; > > err_put_file: > - fput(file); > + fput(anon_file->file); > + anon_file->file = NULL; When cachefiles_ondemand_get_fd() returns failure, anon_file->file is not used, and thus I don't think it is worth resetting anon_file->file to NULL. Or we could assign fd and struct file at the very end when all succeed. > err_put_fd: > - put_unused_fd(fd); > + put_unused_fd(anon_file->fd); > + anon_file->fd = ret; Ditto. > err_free_id: > xa_erase(&cache->ondemand_ids, object_id); > err: > @@ -376,6 +382,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, > struct cachefiles_msg *msg; > size_t n; > int ret = 0; > + struct anon_file anon_file; > XA_STATE(xas, &cache->reqs, cache->req_id_next); > > xa_lock(&cache->reqs); > @@ -409,7 +416,7 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, > xa_unlock(&cache->reqs); > > if (msg->opcode == CACHEFILES_OP_OPEN) { > - ret = cachefiles_ondemand_get_fd(req); > + ret = cachefiles_ondemand_get_fd(req, &anon_file); > if (ret) > goto out; > } > @@ -417,10 +424,16 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, > msg->msg_id = xas.xa_index; > msg->object_id = req->object->ondemand->ondemand_id; > > - if (copy_to_user(_buffer, msg, n) != 0) { > + if (copy_to_user(_buffer, msg, n) != 0) > ret = -EFAULT; > - if (msg->opcode == CACHEFILES_OP_OPEN) > - close_fd(((struct cachefiles_open *)msg->data)->fd); > + > + if (msg->opcode == CACHEFILES_OP_OPEN) { > + if (ret < 0) { > + fput(anon_file.file); > + put_unused_fd(anon_file.fd); > + goto out; > + } > + fd_install(anon_file.fd, anon_file.file); > } > out: > cachefiles_put_object(req->object, cachefiles_obj_put_read_req); -- Thanks, Jingbo