linux-kernel - Re: [PATCH] Add security.selinux XATTR support for the UBIFS. Also fix couple of bugs in UBIFS extended attribute length calculation.

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Date:	Mon, 09 Apr 2012 09:42:35 -0400
From:	David Quigley <selinux@...equigley.com>
To:	Casey Schaufler <casey@...aufler-ca.com>
Cc:	Subodh Nijsure <subodh.nijsure@...il.com>,
	<linux-mtd@...ts.infradead.org>,
	Artem Bityutskiy <dedekind1@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	<linux-kernel@...r.kernel.org>,
	Subodh Nijsure <snijsure@...d-net.com>,
	LSM <linux-security-module@...r.kernel.org>,
	SE Linux <selinux@...ho.nsa.gov>
Subject: Re: [PATCH] Add security.selinux XATTR support for the UBIFS. Also
 fix couple of bugs in UBIFS extended attribute length calculation.

On 04/08/2012 22:37, Casey Schaufler wrote:
>> +
>> +size_t
>> +ubifs_security_listxattr(struct dentry *d, char *list, size_t 
>> list_size,
>> +			 const char *name, size_t name_len, int flags)
>> +{
>> +	const int prefix_len = XATTR_SECURITY_PREFIX_LEN;
>> +	const size_t total_len = prefix_len + name_len + 1;
>> +	if (list && total_len <= list_size) {
>> +		memcpy(list, XATTR_SECURITY_PREFIX, prefix_len);
>> +		memcpy(list+prefix_len, name, name_len);
>> +		list[prefix_len + name_len] = '\0';
>> +	}
>> +	return total_len;
>> +}
>> +
>> +
>> +int ubifs_security_getxattr(struct dentry *d, const char *name,
>> +			    void *buffer, size_t size, int flags)
>> +{
>> +	if (strcmp(name, "") == 0)
>> +		return -EINVAL;
>> +	return __ubifs_getxattr(d->d_inode, XATTR_NAME_SELINUX, buffer, 
>> size);
>> +}
>> +
>> +
>> +int ubifs_security_setxattr(struct dentry *d, const char *name,
>> +			    const void *value, size_t size,
>> +			    int flags, int handler_flags)
>> +{
>> +	if (strcmp(name, "") == 0)
>> +		return -EINVAL;
>> +	return __ubifs_setxattr(d->d_inode, XATTR_NAME_SELINUX, value,

More constructively, Casey is right in that you shouldn't be putting 
the SELinux xattr in there. If __ubifs_setxattr is expecting the full 
namespace.name string just pass name down. Otherwise strip off the 
security. and send the remaining porting down to __ubiffs_setxattr.

Dave
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