lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 6 May 2024 10:31:04 +0800
From: Jingbo Xu <jefflexu@...ux.alibaba.com>
To: libaokun@...weicloud.com, netfs@...ts.linux.dev
Cc: dhowells@...hat.com, jlayton@...nel.org, zhujia.zj@...edance.com,
 linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 06/12] cachefiles: add consistency check for copen/cread

Hi Baokun,

Thanks for improving on this!

On 4/24/24 11:39 AM, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> This prevents malicious processes from completing random copen/cread
> requests and crashing the system. Added checks are listed below:
> 
>   * Generic, copen can only complete open requests, and cread can only
>     complete read requests.
>   * For copen, ondemand_id must not be 0, because this indicates that the
>     request has not been read by the daemon.
>   * For cread, the object corresponding to fd and req should be the same.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> ---
>  fs/cachefiles/ondemand.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
> index bb94ef6a6f61..898fab68332b 100644
> --- a/fs/cachefiles/ondemand.c
> +++ b/fs/cachefiles/ondemand.c
> @@ -82,12 +82,12 @@ static loff_t cachefiles_ondemand_fd_llseek(struct file *filp, loff_t pos,
>  }
>  
>  static long cachefiles_ondemand_fd_ioctl(struct file *filp, unsigned int ioctl,
> -					 unsigned long arg)
> +					 unsigned long id)
>  {
>  	struct cachefiles_object *object = filp->private_data;
>  	struct cachefiles_cache *cache = object->volume->cache;
>  	struct cachefiles_req *req;
> -	unsigned long id;
> +	XA_STATE(xas, &cache->reqs, id);
>  
>  	if (ioctl != CACHEFILES_IOC_READ_COMPLETE)
>  		return -EINVAL;
> @@ -95,10 +95,15 @@ static long cachefiles_ondemand_fd_ioctl(struct file *filp, unsigned int ioctl,
>  	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
>  		return -EOPNOTSUPP;
>  
> -	id = arg;
> -	req = xa_erase(&cache->reqs, id);
> -	if (!req)
> +	xa_lock(&cache->reqs);
> +	req = xas_load(&xas);
> +	if (!req || req->msg.opcode != CACHEFILES_OP_READ ||
> +	    req->object != object) {
> +		xa_unlock(&cache->reqs);
>  		return -EINVAL;
> +	}
> +	xas_store(&xas, NULL);
> +	xa_unlock(&cache->reqs);
>  
>  	trace_cachefiles_ondemand_cread(object, id);
>  	complete(&req->done);
> @@ -126,6 +131,7 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
>  	unsigned long id;
>  	long size;
>  	int ret;
> +	XA_STATE(xas, &cache->reqs, 0);
>  
>  	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
>  		return -EOPNOTSUPP;
> @@ -149,9 +155,16 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
>  	if (ret)
>  		return ret;
>  
> -	req = xa_erase(&cache->reqs, id);
> -	if (!req)
> +	xa_lock(&cache->reqs);
> +	xas.xa_index = id;
> +	req = xas_load(&xas);
> +	if (!req || req->msg.opcode != CACHEFILES_OP_OPEN ||
> +	    !req->object->ondemand->ondemand_id) {
> +		xa_unlock(&cache->reqs);
>  		return -EINVAL;
> +	}
> +	xas_store(&xas, NULL);
> +	xa_unlock(&cache->reqs);
>  
>  	/* fail OPEN request if copen format is invalid */
>  	ret = kstrtol(psize, 0, &size);

The code looks good to me, but I still have some questions.

First, what's the worst consequence if the daemon misbehaves like
completing random copen/cread requests? I mean, does that affect other
processes on the system besides the direct users of the ondemand mode,
e.g. will the misbehavior cause system crash?

Besides, it seems that the above security improvement is only "best
effort".  It can not completely prevent a malicious misbehaved daemon
from completing random copen/cread requests, right?

-- 
Thanks,
Jingbo

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ