The patch titled
unprivileged mounts: allow unprivileged mounts
has been added to the -mm tree. Its filename is
unprivileged-mounts-allow-unprivileged-mounts.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: unprivileged mounts: allow unprivileged mounts
From: Miklos Szeredi <mszeredi@xxxxxxx>
Define a new fs flag FS_SAFE, which denotes, that unprivileged mounting of
this filesystem may not constitute a security problem.
Since most filesystems haven't been designed with unprivileged mounting in
mind, a thorough audit is needed before setting this flag.
For "safe" filesystems also allow unprivileged forced unmounting.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Ram Pai <linuxram@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 54 +++++++++++++++++++++++++++++++------------
include/linux/fs.h | 1
2 files changed, 41 insertions(+), 14 deletions(-)
diff -puN fs/namespace.c~unprivileged-mounts-allow-unprivileged-mounts fs/namespace.c
--- a/fs/namespace.c~unprivileged-mounts-allow-unprivileged-mounts
+++ a/fs/namespace.c
@@ -705,14 +705,16 @@ static bool is_mount_owner(struct vfsmou
/*
* umount is permitted for
* - sysadmin
- * - mount owner, if not forced umount
+ * - mount owner
+ * o if not forced umount,
+ * o if forced umount, and filesystem is "safe"
*/
static bool permit_umount(struct vfsmount *mnt, int flags)
{
if (capable(CAP_SYS_ADMIN))
return true;
- if (flags & MNT_FORCE)
+ if ((flags & MNT_FORCE) && !(mnt->mnt_sb->s_type->fs_flags & FS_SAFE))
return false;
return is_mount_owner(mnt, current->fsuid);
@@ -768,13 +770,17 @@ asmlinkage long sys_oldumount(char __use
* - mountpoint is not a symlink
* - mountpoint is in a mount owned by the user
*/
-static bool permit_mount(struct nameidata *nd, int *flags)
+static bool permit_mount(struct nameidata *nd, struct file_system_type *type,
+ int *flags)
{
struct inode *inode = nd->dentry->d_inode;
if (capable(CAP_SYS_ADMIN))
return true;
+ if (type && !(type->fs_flags & FS_SAFE))
+ return false;
+
if (S_ISLNK(inode->i_mode))
return false;
@@ -1008,7 +1014,7 @@ static int do_loopback(struct nameidata
struct vfsmount *mnt = NULL;
int err;
- if (!permit_mount(nd, &flags))
+ if (!permit_mount(nd, NULL, &flags))
return -EPERM;
if (!old_name || !*old_name)
return -EINVAL;
@@ -1169,26 +1175,46 @@ out:
* create a new mount for userspace and request it to be added into the
* namespace's tree
*/
-static int do_new_mount(struct nameidata *nd, char *type, int flags,
+static int do_new_mount(struct nameidata *nd, char *fstype, int flags,
int mnt_flags, char *name, void *data)
{
+ int err;
struct vfsmount *mnt;
+ struct file_system_type *type;
- if (!type || !memchr(type, 0, PAGE_SIZE))
+ if (!fstype || !memchr(fstype, 0, PAGE_SIZE))
return -EINVAL;
- /* we need capabilities... */
- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
-
- mnt = do_kern_mount(type, flags & ~MS_SETUSER, name, data);
- if (IS_ERR(mnt))
+ type = get_fs_type(fstype);
+ if (!type)
+ return -ENODEV;
+
+ err = -EPERM;
+ if (!permit_mount(nd, type, &flags))
+ goto out_put_filesystem;
+
+ if (flags & MS_SETUSER) {
+ err = reserve_user_mount();
+ if (err)
+ goto out_put_filesystem;
+ }
+
+ mnt = vfs_kern_mount(type, flags & ~MS_SETUSER, name, data);
+ put_filesystem(type);
+ if (IS_ERR(mnt)) {
+ if (flags & MS_SETUSER)
+ dec_nr_user_mounts();
return PTR_ERR(mnt);
+ }
if (flags & MS_SETUSER)
- set_mnt_user(mnt);
+ __set_mnt_user(mnt);
return do_add_mount(mnt, nd, mnt_flags, NULL);
+
+ out_put_filesystem:
+ put_filesystem(type);
+ return err;
}
/*
@@ -1218,7 +1244,7 @@ int do_add_mount(struct vfsmount *newmnt
if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
goto unlock;
- /* MNT_USER was set earlier */
+ /* some flags may have been set earlier */
newmnt->mnt_flags |= mnt_flags;
if ((err = graft_tree(newmnt, nd)))
goto unlock;
diff -puN include/linux/fs.h~unprivileged-mounts-allow-unprivileged-mounts include/linux/fs.h
--- a/include/linux/fs.h~unprivileged-mounts-allow-unprivileged-mounts
+++ a/include/linux/fs.h
@@ -96,6 +96,7 @@ extern int dir_notify_enable;
#define FS_REQUIRES_DEV 1
#define FS_BINARY_MOUNTDATA 2
#define FS_HAS_SUBTYPE 4
+#define FS_SAFE 8 /* Safe to mount by unprivileged users */
#define FS_REVAL_DOT 16384 /* Check the paths ".", ".." for staleness */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move()
* during rename() internally.
_
Patches currently in -mm which might be from mszeredi@xxxxxxx are
split-mmap.patch
only-allow-nonlinear-vmas-for-ram-backed-filesystems.patch
fix-quadratic-behavior-of-shrink_dcache_parent.patch
mm-shrink-parent-dentries-when-shrinking-slab.patch
add-filesystem-subtype-support.patch
add-file-position-info-to-proc.patch
check-privileges-before-setting-mount-propagation.patch
consolidate-generic_writepages-and-mpage_writepages.patch
unprivileged-mounts-add-user-mounts-to-the-kernel.patch
unprivileged-mounts-allow-unprivileged-umount.patch
unprivileged-mounts-account-user-mounts.patch
unprivileged-mounts-propagate-error-values-from-clone_mnt.patch
unprivileged-mounts-allow-unprivileged-bind-mounts.patch
unprivileged-mounts-put-declaration-of-put_filesystem-in-fsh.patch
unprivileged-mounts-allow-unprivileged-mounts.patch
unprivileged-mounts-allow-unprivileged-fuse-mounts.patch
unprivileged-mounts-propagation-inherit-owner-from-parent.patch
unprivileged-mounts-add-no-submounts-flag.patch
-
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