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SubjectRe: [Patch 1/2] selinux: ajust rules for ATTR_FORCE
Date
Stephen Smalley <sds@tycho.nsa.gov> writes:

> On Mon, 2009-08-17 at 03:07 -0400, Amerigo Wang wrote:
>> 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.

[...]

>
> This will only apply the setattr check if ATTR_FORCE was specified,
> which is not the current behavior nor what we want.
>
> NAK.

How about this? I tweaked Amerigo's patch, and it is based on the
original code is doing. This is only compile-test though.

[I'm still not sure what selinux want to do. normally inode_permission()
should check truncate() permission, and this FILE__SIZE checks something
again...? And we want to check FILE__WRITE for ATTR_[AMC]TIME?]

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

[PATCH] selinux: adjust rules for ATTR_FORCE

From: Amerigo Wang <amwang@redhat.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@tycho.nsa.gov>
Cc: Eric Paris <eparis@redhat.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
[tweaks]
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---

security/selinux/hooks.c | 28 ++++++++++++++++++++--------
1 file changed, 20 insertions(+), 8 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 01:01:13.000000000 +0900
+++ linux-2.6-hirofumi/security/selinux/hooks.c 2009-08-18 03:23:52.000000000 +0900
@@ -2710,16 +2710,28 @@ static int selinux_inode_permission(stru

static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
{
- const struct cred *cred = current_cred();
-
- if (iattr->ia_valid & ATTR_FORCE)
- return 0;
+#define SELINUX_F_SETATTR_MASK (ATTR_MODE | ATTR_UID | ATTR_GID | \
+ ATTR_ATIME_SET | ATTR_MTIME_SET | \
+ ATTR_TIMES_SET)
+#define SELINUX_F_WRITE_MASK (ATTR_CTIME | ATTR_MTIME | ATTR_ATIME | \
+ ATTR_SIZE)

- if (iattr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID |
- ATTR_ATIME_SET | ATTR_MTIME_SET))
- return dentry_has_perm(cred, NULL, dentry, FILE__SETATTR);
+ const struct cred *cred = current_cred();
+ unsigned int ia_valid = iattr->ia_valid;

- return dentry_has_perm(cred, NULL, dentry, FILE__WRITE);
+ if (!(ia_valid & ATTR_FORCE) && (ia_valid & SELINUX_F_SETATTR_MASK)) {
+ int err = dentry_has_perm(cred, NULL, dentry, FILE__SETATTR);
+ if (err)
+ return err;
+ /* Assume timestamp was changed by attributes or utimes(). */
+ ia_valid &= ~(ATTR_CTIME | ATTR_MTIME | ATTR_ATIME);
+ }
+ if (ia_valid & SELINUX_F_WRITE_MASK) {
+ int err = dentry_has_perm(cred, NULL, dentry, FILE__WRITE);
+ if (err)
+ return err;
+ }
+ return 0;
}

static int selinux_inode_getattr(struct vfsmount *mnt, struct dentry *dentry)
_

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