linux-kernel - Re: [PATCH v3 1/1] ovl: setxattr: don't deadlock when called from ima_fix

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Date:	Mon, 30 May 2016 22:15:31 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>, Krisztian Litkey <kli@....fi>,
	linux-unionfs@...r.kernel.org,
	Krisztian Litkey <krisztian.litkey@...el.com>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] ovl: setxattr: don't deadlock when called from
 ima_fix_xattr.

On Mon, 2016-05-30 at 17:50 +0100, Al Viro wrote:
> 	Only tangentially related, but... that bug had been discussed,
> without any results: the fallback in ima_d_path() to ->d_name.name is
> completely broken.  There is no warranty whatsoever that dentry won't be
> renamed, with its earlier (too long to be embedded into dentry itself)
> ->d_name.name getting freed.  Right under your code.

Isn't i_mutex required?

> 
> 	Could we please get rid of that thing?  "A message in a near-oom
> situation might be less informative than we'd like" is better than
> "this code might end up dereferencing freed memory".
> 
> 	Another similar bug is in ima_collect_measurement() -
>         const char *filename = file->f_path.dentry->d_name.name;
> 	...
>                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
>                                     filename, "collect_data", audit_cause,
> with no warranty whatsoever that you are not passing a pointer to freed
> memory.  The same goes for ima_eventname_init_common() -
>         if (event_data->file) {
>                 cur_filename = event_data->file->f_path.dentry->d_name.name;
>                 cur_filename_len = strlen(cur_filename);
>         } else  
> ...
>         return ima_write_template_field_data(cur_filename, cur_filename_len,
>                                              DATA_FMT_STRING, field_data);
> --
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