linux-kernel - Re: [Patch 1/2] selinux: ajust rules for ATTR

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Date:	Tue, 18 Aug 2009 16:39:00 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Amerigo Wang <amwang@...hat.com>
Cc:	Stephen Smalley <sds@...ho.nsa.gov>, linux-kernel@...r.kernel.org,
	esandeen@...hat.com, eteo@...hat.com, eparis@...hat.com,
	linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
	viro@...iv.linux.org.uk
Subject: Re: [Patch 1/2] selinux: ajust rules for ATTR_FORCE

[Sorry if this killed thread. My ISP seems to be stopping email server
now. I've read this email from web archive.]

>> @@ -2711,12 +2711,17 @@ static int selinux_inode_permission(stru
>>  static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
>>  {
>>  	const struct cred *cred = current_cred();
>> +	unsigned int ia_valid = iattr->ia_valid;
>>  
>> -	if (iattr->ia_valid & ATTR_FORCE)
>> -		return 0;
>> +	/* ATTR_FORCE is just used for ATTR_KILL_S[UG]ID. */
>> +	if (ia_valid & ATTR_FORCE) {
>> +		ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE);
>> +		if (!ia_valid)
>> +			return 0;
>>   
> 
> So if I read this correctly, (ATTR_FORCE| ATTR_KILL_SUID|ATTR_MODE) will 
> not return here, since 'ia_valid' will be ATTR_FORCE finally.
> 
> I think you forgot to clear ATTR_FORCE here...

Whoops, good catch. Fortunately, it doesn't seem to have actual problem,
but it's bug obviously, and sorry for that. Fixed patch was attached.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>


[PATCH] selinux: adjust rules for ATTR_FORCE

From: Amerigo Wang <amwang@...hat.com>

As suggested by OGAWA Hirofumi in thread: http://lkml.org/lkml/2009/8/7/132,
we should let selinux_inode_setattr() to match our ATTR_* rules.
ATTR_FORCE should not force things like ATTR_SIZE.

Cc: Stephen Smalley <sds@...ho.nsa.gov>
Cc: Eric Paris <eparis@...hat.com>
Signed-off-by: WANG Cong <amwang@...hat.com>
[tweaks]
Signed-off-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
---

 security/selinux/hooks.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff -puN security/selinux/hooks.c~selinux-truncate-fix security/selinux/hooks.c
--- linux-2.6/security/selinux/hooks.c~selinux-truncate-fix	2009-08-18 06:27:58.000000000 +0900
+++ linux-2.6-hirofumi/security/selinux/hooks.c	2009-08-18 16:10:50.000000000 +0900
@@ -2711,12 +2711,18 @@ static int selinux_inode_permission(stru
 static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
 {
 	const struct cred *cred = current_cred();
+	unsigned int ia_valid = iattr->ia_valid;
 
-	if (iattr->ia_valid & ATTR_FORCE)
-		return 0;
+	/* ATTR_FORCE is just used for ATTR_KILL_S[UG]ID. */
+	if (ia_valid & ATTR_FORCE) {
+		ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE |
+			      ATTR_FORCE);
+		if (!ia_valid)
+			return 0;
+	}
 
-	if (iattr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
-			       ATTR_ATIME_SET | ATTR_MTIME_SET))
+	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
+			ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_TIMES_SET))
 		return dentry_has_perm(cred, NULL, dentry, FILE__SETATTR);
 
 	return dentry_has_perm(cred, NULL, dentry, FILE__WRITE);
_
--
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