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Date: Wed, 15 Jan 2014 05:53:36 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: miklos@...redi.hu
Cc: john.johansen@...onical.com, mszeredi@...e.cz,
linux-security-module@...r.kernel.org, viro@...iv.linux.org.uk,
torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, hch@...radead.org,
akpm@...ux-foundation.org, dhowells@...hat.com, zab@...hat.com,
jack@...e.cz, luto@...capital.net
Subject: Re: [PATCH 00/11] cross rename v3
John Johansen wrote:
> On 01/14/2014 05:03 AM, Tetsuo Handa wrote:
> > Miklos Szeredi wrote:
> >> On Mon, Jan 13, 2014 at 11:03 PM, Tetsuo Handa
> >> <penguin-kernel@...ove.sakura.ne.jp> wrote:
> >>> Miklos Szeredi wrote:
> >>>> Cross rename (A, B) is equivalent to plain rename(A, B) + plain rename
> >>>> (B, A) done as a single atomic operation. If security module allows
> >>>> both then cross rename is allowed. If at least one is denied then the
> >>>> cross rename is denied.
> >>>
> >>> Yes, the functionality itself is fine. The problem is how LSM users check
> >>> their permissions for the functionality.
> >>>
> >>>>
> >>>> This is prepared for in "[PATCH 06/11] security: add flags to rename
> >>>> hooks" and actually done in "[PATCH 07/11] vfs: add cross-rename".
> >>>>
> >>>> Security people are free to implement a explicit security check for
> >>>> cross rename, but I don't think that is in the scope of this patchset.
> >>>>
> >>> I don't know how their permissions are checked, but I think that
> >>> swapping /A/B and /C/D should check not only
> >>>
> >>> Remove a name from directory A
> >>> Add a name to directory C
> >>>
> >>> but also
> >>>
> >>> Add a name to directory A
> >>> Remove a name from directory C
> >>>
> >>> using their security labels.
> >>>
> >>> Without making changes to security/*/ directory, SELinux/SMACK/TOMOYO/AppArmor
> >>> might fail to check the latter permissions.
> >>
> >> Those permissions will be checked. Please see security/security.c in
> >> patch 07/11 of the series.
> >>
> > Oh, I see. But I think that 07/11 is wasteful for security_path_rename() users.
> > Why bother to re-calculate /A/B and /C/D using d_absolute_path()?
> >
> > I prefer flags argument passed to tomoyo_path_rename(). Untested patch follows.
> > John, what about AppArmor?
>
> Right policy wise it doesn't make a difference but not having to re-calculate
> the paths would be more efficient.
>
> I'd re-factor the apparmor bit of the patch differently so that the paths aren't
> recomputed, what is in the patch looks like it should work. In fact I would want
> to do the apparmor refactor as a separate patch so that the internal changes
> needed to take advantage of the LSM change are separate from the LSM change
> it self.
>
> I've only given the patch a quick once over and not tested it yet, but it looks
> good, so far.
I see. And security_inode_rename() should also receive the flags argument, for
smack_inode_rename() needs no change as it checks MAY_READWRITE permission on
both inodes.
I think below change is fine for SELinux/SMACK/Capability. TOMOYO and AppArmor
want separate patch for RENAME_EXCHANGE handling.
Miklos, can you insert below change between a patch which defines
RENAME_EXCHANGE and a patch which implements RENAME_EXCHANGE functionality?
diff --git a/include/linux/security.h b/include/linux/security.h
index 95cfccc..dbd05ca 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -446,6 +446,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* @old_dentry contains the dentry structure of the old link.
* @new_dir contains the inode structure for parent of the new link.
* @new_dentry contains the dentry structure of the new link.
+ * @flags contains rename flags.
* Return 0 if permission is granted.
* @path_rename:
* Check for permission to rename a file or directory.
@@ -453,6 +454,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* @old_dentry contains the dentry structure of the old link.
* @new_dir contains the path structure for parent of the new link.
* @new_dentry contains the dentry structure of the new link.
+ * @flags contains rename flags.
* Return 0 if permission is granted.
* @path_chmod:
* Check for permission to change DAC's permission of a file or directory.
@@ -1491,7 +1493,8 @@ struct security_operations {
int (*path_link) (struct dentry *old_dentry, struct path *new_dir,
struct dentry *new_dentry);
int (*path_rename) (struct path *old_dir, struct dentry *old_dentry,
- struct path *new_dir, struct dentry *new_dentry);
+ struct path *new_dir, struct dentry *new_dentry,
+ unsigned int flags);
int (*path_chmod) (struct path *path, umode_t mode);
int (*path_chown) (struct path *path, kuid_t uid, kgid_t gid);
int (*path_chroot) (struct path *path);
@@ -1514,7 +1517,8 @@ struct security_operations {
int (*inode_mknod) (struct inode *dir, struct dentry *dentry,
umode_t mode, dev_t dev);
int (*inode_rename) (struct inode *old_dir, struct dentry *old_dentry,
- struct inode *new_dir, struct dentry *new_dentry);
+ struct inode *new_dir, struct dentry *new_dentry,
+ unsigned int flags);
int (*inode_readlink) (struct dentry *dentry);
int (*inode_follow_link) (struct dentry *dentry, struct nameidata *nd);
int (*inode_permission) (struct inode *inode, int mask);
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 4257b7e..2afa7c5 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -315,7 +315,8 @@ static int apparmor_path_link(struct dentry *old_dentry, struct path *new_dir,
}
static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
- struct path *new_dir, struct dentry *new_dentry)
+ struct path *new_dir, struct dentry *new_dentry,
+ unsigned int flags)
{
struct aa_profile *profile;
int error = 0;
diff --git a/security/capability.c b/security/capability.c
index 8b4f24a..ab2f231 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -176,7 +176,8 @@ static int cap_inode_mknod(struct inode *inode, struct dentry *dentry,
}
static int cap_inode_rename(struct inode *old_inode, struct dentry *old_dentry,
- struct inode *new_inode, struct dentry *new_dentry)
+ struct inode *new_inode, struct dentry *new_dentry,
+ unsigned int flags)
{
return 0;
}
@@ -280,7 +281,8 @@ static int cap_path_link(struct dentry *old_dentry, struct path *new_dir,
}
static int cap_path_rename(struct path *old_path, struct dentry *old_dentry,
- struct path *new_path, struct dentry *new_dentry)
+ struct path *new_path, struct dentry *new_dentry,
+ unsigned int flags)
{
return 0;
}
diff --git a/security/security.c b/security/security.c
index 3dd2258..f90ac9b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -440,15 +440,8 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
(new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
return 0;
- if (flags & RENAME_EXCHANGE) {
- int err = security_ops->path_rename(new_dir, new_dentry,
- old_dir, old_dentry);
- if (err)
- return err;
- }
-
return security_ops->path_rename(old_dir, old_dentry, new_dir,
- new_dentry);
+ new_dentry, flags);
}
EXPORT_SYMBOL(security_path_rename);
@@ -540,15 +533,8 @@ int security_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
(new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
return 0;
- if (flags & RENAME_EXCHANGE) {
- int err = security_ops->inode_rename(new_dir, new_dentry,
- old_dir, old_dentry);
- if (err)
- return err;
- }
-
return security_ops->inode_rename(old_dir, old_dentry,
- new_dir, new_dentry);
+ new_dir, new_dentry, flags);
}
int security_inode_readlink(struct dentry *dentry)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3219560..fffd458 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2714,9 +2714,13 @@ static int selinux_inode_mknod(struct inode *dir, struct dentry *dentry, umode_t
}
static int selinux_inode_rename(struct inode *old_inode, struct dentry *old_dentry,
- struct inode *new_inode, struct dentry *new_dentry)
+ struct inode *new_inode, struct dentry *new_dentry,
+ unsigned int flags)
{
- return may_rename(old_inode, old_dentry, new_inode, new_dentry);
+ int err = may_rename(old_inode, old_dentry, new_inode, new_dentry);
+ if (!err && (flags & RENAME_EXCHANGE))
+ err = may_rename(new_inode, new_dentry, old_inode, old_dentry);
+ return err;
}
static int selinux_inode_readlink(struct dentry *dentry)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index d814e35..623fce6 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -697,6 +697,7 @@ static int smack_inode_rmdir(struct inode *dir, struct dentry *dentry)
* @old_dentry: unused
* @new_inode: the new directory
* @new_dentry: unused
+ * @flags: rename flags
*
* Read and write access is required on both the old and
* new directories.
@@ -706,7 +707,8 @@ static int smack_inode_rmdir(struct inode *dir, struct dentry *dentry)
static int smack_inode_rename(struct inode *old_inode,
struct dentry *old_dentry,
struct inode *new_inode,
- struct dentry *new_dentry)
+ struct dentry *new_dentry,
+ unsigned int flags)
{
int rc;
char *isp;
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index f0b756e..ac7dd97 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -287,13 +287,15 @@ static int tomoyo_path_link(struct dentry *old_dentry, struct path *new_dir,
* @old_dentry: Pointer to "struct dentry".
* @new_parent: Pointer to "struct path".
* @new_dentry: Pointer to "struct dentry".
+ * @flags: Rename flags.
*
* Returns 0 on success, negative value otherwise.
*/
static int tomoyo_path_rename(struct path *old_parent,
struct dentry *old_dentry,
struct path *new_parent,
- struct dentry *new_dentry)
+ struct dentry *new_dentry,
+ unsigned int flags)
{
struct path path1 = { old_parent->mnt, old_dentry };
struct path path2 = { new_parent->mnt, new_dentry };
--
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