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Commit 9b40bc90 authored by Al Viro's avatar Al Viro
Browse files

get rid of unprotected dereferencing of mnt->mnt_ns 



It's safe only under namespace_sem or vfsmount_lock; all places
in fs/namespace.c that want mnt->mnt_ns->user_ns actually want to use
current->nsproxy->mnt_ns->user_ns (note the calls of check_mnt() in
there).

Cc: stable@vger.kernel.org
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 3a142ed9

fs/namespace.c

+17 −12
Original line number Diff line number Diff line
@@ -1237,6 +1237,14 @@ static int do_umount(struct mount *mnt, int flags) 
	return retval;

}



/* 

 * Is the caller allowed to modify his namespace?

 */

static inline bool may_mount(void)

{

	return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);

}



/*

 * Now umount can handle mount points as well as block devices.

 * This is important for filesystems which use unnamed block devices.
@@ -1255,6 +1263,9 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) 
	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))

		return -EINVAL;



	if (!may_mount())

		return -EPERM;



	if (!(flags & UMOUNT_NOFOLLOW))

		lookup_flags |= LOOKUP_FOLLOW;
@@ -1268,10 +1279,6 @@ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) 
	if (!check_mnt(mnt))

		goto dput_and_out;



	retval = -EPERM;

	if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN))

		goto dput_and_out;



	retval = do_umount(mnt, flags);

dput_and_out:

	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
@@ -1295,7 +1302,7 @@ SYSCALL_DEFINE1(oldumount, char __user *, name) 


static int mount_is_safe(struct path *path)

{

	if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN))

	if (may_mount())

		return 0;

	return -EPERM;

#ifdef notyet
@@ -1633,7 +1640,7 @@ static int do_change_type(struct path *path, int flag) 
	int type;

	int err = 0;



	if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN))

	if (!may_mount())

		return -EPERM;



	if (path->dentry != path->mnt->mnt_root)
@@ -1797,7 +1804,7 @@ static int do_move_mount(struct path *path, const char *old_name) 
	struct mount *p;

	struct mount *old;

	int err = 0;

	if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN))

	if (!may_mount())

		return -EPERM;

	if (!old_name || !*old_name)

		return -EINVAL;
@@ -1933,16 +1940,14 @@ static int do_new_mount(struct path *path, const char *fstype, int flags, 
			int mnt_flags, const char *name, void *data)

{

	struct file_system_type *type;

	struct user_namespace *user_ns;

	struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;

	struct vfsmount *mnt;

	int err;



	if (!fstype)

		return -EINVAL;



	/* we need capabilities... */

	user_ns = real_mount(path->mnt)->mnt_ns->user_ns;

	if (!ns_capable(user_ns, CAP_SYS_ADMIN))

	if (!may_mount())

		return -EPERM;



	type = get_fs_type(fstype);
@@ -2567,7 +2572,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 
	struct mount *new_mnt, *root_mnt;

	int error;



	if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))

	if (!may_mount())

		return -EPERM;



	error = user_path_dir(new_root, &new);