[PATCH][SELINUX] Fix selinux_inode_setattr hook

[PATCH][SELINUX] Fix selinux_inode_setattr hook

[Stephen Smalley]

This patch against 2.6.11-rc3 fixes the selinux_inode_setattr hook
function to honor the ATTR_FORCE flag, skipping any permission checking
in that case.  Otherwise, it is possible though unlikely for a denial
from the hook to prevent proper updating, e.g. for remove_suid upon
writing to a file.  This would only occur if the process had write
permission to a suid file but lacked setattr permission to it.  Please
apply.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@redhat.com>

 security/selinux/hooks.c |    3 +++
 1 files changed, 3 insertions(+)

Index: linux-2.6/security/selinux/hooks.c
===================================================================
RCS file: /nfshome/pal/CVS/linux-2.6/security/selinux/hooks.c,v
retrieving revision 1.150
diff -u -p -r1.150 hooks.c
--- linux-2.6/security/selinux/hooks.c	26 Jan 2005 21:20:59 -0000	1.150
+++ linux-2.6/security/selinux/hooks.c	4 Feb 2005 16:39:23 -0000
@@ -2142,6 +2142,9 @@ static int selinux_inode_setattr(struct 
 	if (rc)
 		return rc;
 
+	if (iattr->ia_valid & ATTR_FORCE)
+		return 0;
+
 	if (iattr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
 			       ATTR_ATIME_SET | ATTR_MTIME_SET))
 		return dentry_has_perm(current, NULL, dentry, FILE__SETATTR);


-- 
Stephen Smalley <sds@tycho.nsa.gov>
National Security Agency

Re: [PATCH][SELINUX] Fix selinux_inode_setattr hook

[Stephen Smalley]

On Fri, 2005-02-04 at 13:14, Chris Wright wrote:
> * Stephen Smalley (sds@tycho.nsa.gov) wrote:
> > This patch against 2.6.11-rc3 fixes the selinux_inode_setattr hook
> > function to honor the ATTR_FORCE flag, skipping any permission checking
> > in that case.  Otherwise, it is possible though unlikely for a denial
> > from the hook to prevent proper updating, e.g. for remove_suid upon
> > writing to a file.  This would only occur if the process had write
> > permission to a suid file but lacked setattr permission to it.  Please
> > apply.
> 
> Is there any reason not to promote this to the framework?

I wasn't sure if a security module might still want to be notified of
forced changes (e.g. to adjust some state in its own security
structure), even if it skips permission checking on such changes.

-- 
Stephen Smalley <sds@tycho.nsa.gov>
National Security Agency

Re: [PATCH][SELINUX] Fix selinux_inode_setattr hook

[Chris Wright]

* Stephen Smalley (sds@tycho.nsa.gov) wrote:
> This patch against 2.6.11-rc3 fixes the selinux_inode_setattr hook
> function to honor the ATTR_FORCE flag, skipping any permission checking
> in that case.  Otherwise, it is possible though unlikely for a denial
> from the hook to prevent proper updating, e.g. for remove_suid upon
> writing to a file.  This would only occur if the process had write
> permission to a suid file but lacked setattr permission to it.  Please
> apply.

Is there any reason not to promote this to the framework?

thanks,
-chris
-- 
Linux Security Modules     http://lsm.immunix.org     http://lsm.bkbits.net

Re: [PATCH][SELINUX] Fix selinux_inode_setattr hook

[Chris Wright]

* Stephen Smalley (sds@tycho.nsa.gov) wrote:
> On Fri, 2005-02-04 at 13:14, Chris Wright wrote:
> > * Stephen Smalley (sds@tycho.nsa.gov) wrote:
> > > This patch against 2.6.11-rc3 fixes the selinux_inode_setattr hook
> > > function to honor the ATTR_FORCE flag, skipping any permission checking
> > > in that case.  Otherwise, it is possible though unlikely for a denial
> > > from the hook to prevent proper updating, e.g. for remove_suid upon
> > > writing to a file.  This would only occur if the process had write
> > > permission to a suid file but lacked setattr permission to it.  Please
> > > apply.
> > 
> > Is there any reason not to promote this to the framework?
> 
> I wasn't sure if a security module might still want to be notified of
> forced changes (e.g. to adjust some state in its own security
> structure), even if it skips permission checking on such changes.

OK, let's go with your patch for now.

thanks,
-chris
-- 
Linux Security Modules     http://lsm.immunix.org     http://lsm.bkbits.net