diff mbox

[3.13.y-ckt,stable] Patch "mnt: Modify fs_fully_visible to deal with locked ro nodev and atime" has been added to staging queue

Message ID 1437616678-19041-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 23, 2015, 1:57 a.m. UTC 
This is a note to let you know that I have just added a patch titled

    mnt: Modify fs_fully_visible to deal with locked ro nodev and atime

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt24.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

From 3242db094b311baf111be51b61989ff9a772dc8e Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xmission.com>
Date: Fri, 8 May 2015 23:49:47 -0500
Subject: mnt: Modify fs_fully_visible to deal with locked ro nodev and atime

commit 8c6cf9cc829fcd0b179b59f7fe288941d0e31108 upstream.

Ignore an existing mount if the locked readonly, nodev or atime
attributes are less permissive than the desired attributes
of the new mount.

On success ensure the new mount locks all of the same readonly, nodev and
atime attributes as the old mount.

The nosuid and noexec attributes are not checked here as this change
is destined for stable and enforcing those attributes causes a
regression in lxc and libvirt-lxc where those applications will not
start and there are no known executables on sysfs or proc and no known
way to create exectuables without code modifications

Fixes: e51db73532955 ("userns: Better restrictions on when proc and sysfs can be mounted")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/namespace.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/fs/namespace.c b/fs/namespace.c
index 09bc75b..dfe193a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2141,7 +2141,7 @@  unlock:
 	return err;
 }

-static bool fs_fully_visible(struct file_system_type *fs_type);
+static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);

 /*
  * create a new mount for userspace and request it to be added into the
@@ -2175,7 +2175,7 @@  static int do_new_mount(struct path *path, const char *fstype, int flags,
 			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
 		}
 		if (type->fs_flags & FS_USERNS_VISIBLE) {
-			if (!fs_fully_visible(type))
+			if (!fs_fully_visible(type, &mnt_flags))
 				return -EPERM;
 		}
 	}
@@ -2996,9 +2996,10 @@  bool current_chrooted(void)
 	return chrooted;
 }

-static bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 {
 	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+	int new_flags = *new_mnt_flags;
 	struct mount *mnt;
 	bool visible = false;

@@ -3017,6 +3018,19 @@  static bool fs_fully_visible(struct file_system_type *type)
 		if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
 			continue;

+		/* Verify the mount flags are equal to or more permissive
+		 * than the proposed new mount.
+		 */
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
+		    !(new_flags & MNT_READONLY))
+			continue;
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
+		    !(new_flags & MNT_NODEV))
+			continue;
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
+		    ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
+			continue;
+
 		/* This mount is not fully visible if there are any child mounts
 		 * that cover anything except for empty directories.
 		 */
@@ -3027,6 +3041,10 @@  static bool fs_fully_visible(struct file_system_type *type)
 			if (inode->i_nlink > 2)
 				goto next;
 		}
+		/* Preserve the locked attributes */
+		*new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \
+							MNT_LOCK_NODEV    | \
+							MNT_LOCK_ATIME);
 		visible = true;
 		goto found;
 	next:	;