linux-kernel - [ 48/59] TOMOYO: Fix mount flags checking order.

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Date:	Wed, 11 Apr 2012 16:11:23 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	James Morris <james.l.morris@...cle.com>
Subject: [ 48/59] TOMOYO: Fix mount flags checking order.

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit df91e49477a9be15921cb2854e1d12a3bdb5e425 upstream.

Userspace can pass in arbitrary combinations of MS_* flags to mount().

If both MS_BIND and one of MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE are
passed, device name which should be checked for MS_BIND was not checked because
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE had higher priority than MS_BIND.

If both one of MS_BIND/MS_MOVE and MS_REMOUNT are passed, device name which
should not be checked for MS_REMOUNT was checked because MS_BIND/MS_MOVE had
higher priority than MS_REMOUNT.

Fix these bugs by changing priority to MS_REMOUNT -> MS_BIND ->
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE -> MS_MOVE as with do_mount() does.

Also, unconditionally return -EINVAL if more than one of
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE is passed so that TOMOYO will not
generate inaccurate audit logs, for commit 7a2e8a8f "VFS: Sanity check mount
flags passed to change_mnt_propagation()" clarified that these flags must be
exclusively passed.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: James Morris <james.l.morris@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/tomoyo/mount.c |   38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

--- a/security/tomoyo/mount.c
+++ b/security/tomoyo/mount.c
@@ -199,30 +199,32 @@ int tomoyo_mount_permission(char *dev_na
 	if (flags & MS_REMOUNT) {
 		type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
 		flags &= ~MS_REMOUNT;
-	}
-	if (flags & MS_MOVE) {
-		type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
-		flags &= ~MS_MOVE;
-	}
-	if (flags & MS_BIND) {
+	} else if (flags & MS_BIND) {
 		type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
 		flags &= ~MS_BIND;
-	}
-	if (flags & MS_UNBINDABLE) {
-		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
-		flags &= ~MS_UNBINDABLE;
-	}
-	if (flags & MS_PRIVATE) {
+	} else if (flags & MS_SHARED) {
+		if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+			return -EINVAL;
+		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
+		flags &= ~MS_SHARED;
+	} else if (flags & MS_PRIVATE) {
+		if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
+			return -EINVAL;
 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
 		flags &= ~MS_PRIVATE;
-	}
-	if (flags & MS_SLAVE) {
+	} else if (flags & MS_SLAVE) {
+		if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
+			return -EINVAL;
 		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
 		flags &= ~MS_SLAVE;
-	}
-	if (flags & MS_SHARED) {
-		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
-		flags &= ~MS_SHARED;
+	} else if (flags & MS_UNBINDABLE) {
+		if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
+			return -EINVAL;
+		type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
+		flags &= ~MS_UNBINDABLE;
+	} else if (flags & MS_MOVE) {
+		type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
+		flags &= ~MS_MOVE;
 	}
 	if (!type)
 		type = "<NULL>";


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