This is a note to let you know that I've just added the patch titled
mnt: Modify fs_fully_visible to deal with locked ro nodev and atime
to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mnt-modify-fs_fully_visible-to-deal-with-locked-ro-nodev-and-atime.patch
and it can be found in the queue-4.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 8c6cf9cc829fcd0b179b59f7fe288941d0e31108 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Date: Fri, 8 May 2015 23:49:47 -0500
Subject: mnt: Modify fs_fully_visible to deal with locked ro nodev and atime
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2334,7 +2334,7 @@ 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
@@ -2368,7 +2368,7 @@ static int do_new_mount(struct path *pat
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;
}
}
@@ -3172,9 +3172,10 @@ 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;
@@ -3193,6 +3194,19 @@ static bool fs_fully_visible(struct file
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
* locked child mounts that cover anything except for
* empty directories.
@@ -3206,6 +3220,10 @@ static bool fs_fully_visible(struct file
if (!is_empty_dir_inode(inode))
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: ;
Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are
queue-4.0/sysfs-create-mountpoints-with-sysfs_create_mount_point.patch
queue-4.0/sysfs-add-support-for-permanently-empty-directories-to-serve-as-mount-points.patch
queue-4.0/mnt-update-fs_fully_visible-to-test-for-permanently-empty-directories.patch
queue-4.0/mnt-refactor-the-logic-for-mounting-sysfs-and-proc-in-a-user-namespace.patch
queue-4.0/mnt-modify-fs_fully_visible-to-deal-with-locked-ro-nodev-and-atime.patch
queue-4.0/fs-add-helper-functions-for-permanently-empty-directories.patch
queue-4.0/sysctl-allow-creating-permanently-empty-directories-that-serve-as-mountpoints.patch
queue-4.0/kernfs-add-support-for-always-empty-directories.patch
queue-4.0/proc-allow-creating-permanently-empty-directories-that-serve-as-mount-points.patch
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