diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 0db9effb18d99e53cf4413c9e0ccb7b09eb58ae2..37fd1fc5396e66f054850a7684b6e531bf3c1cf8 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -400,7 +400,8 @@
386 i386 rseq sys_rseq __ia32_sys_rseq
387 i386 open_tree sys_open_tree __ia32_sys_open_tree
388 i386 move_mount sys_move_mount __ia32_sys_move_mount
-# don't use numbers 389 through 392, add new calls at the end
+389 i386 fsopen sys_fsopen __ia32_sys_fsopen
+# don't use numbers 390 through 392, add new calls at the end
393 i386 semget sys_semget __ia32_sys_semget
394 i386 semctl sys_semctl __ia32_compat_sys_semctl
395 i386 shmget sys_shmget __ia32_sys_shmget
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 0440f0eefa02b69af5fd154ca4b50bfcc6ce11dd..511608a2161153b9690b6ed6357ecec1bb8a3c30 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -345,6 +345,7 @@
334 common rseq __x64_sys_rseq
335 common open_tree __x64_sys_open_tree
336 common move_mount __x64_sys_move_mount
+337 common fsopen __x64_sys_fsopen
# don't use numbers 387 through 423, add new calls after the last
# 'common' entry
424 common pidfd_send_signal __x64_sys_pidfd_send_signal
diff --git a/fs/Makefile b/fs/Makefile
index 35945f8139e61b3c12597211b0a47a011270925f..5a51bc2489ba7bb55bee0594ee70dc4beb7ed187 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -13,7 +13,7 @@ obj-y := open.o read_write.o file_table.o super.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o d_path.o \
stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
- fs_types.o fs_context.o fs_parser.o
+ fs_types.o fs_context.o fs_parser.o fsopen.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 87e3546b9a522dccb030dbc52f78071872e72404..eb806fae311718961a95432c1c7f308f9203eb9e 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -271,6 +271,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
fc->cred = get_current_cred();
fc->net_ns = get_net(current->nsproxy->net_ns);
+ mutex_init(&fc->uapi_mutex);
+
switch (purpose) {
case FS_CONTEXT_FOR_MOUNT:
fc->user_ns = get_user_ns(fc->cred->user_ns);
@@ -353,6 +355,8 @@ struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
if (!fc)
return ERR_PTR(-ENOMEM);
+ mutex_init(&fc->uapi_mutex);
+
fc->fs_private = NULL;
fc->s_fs_info = NULL;
fc->source = NULL;
diff --git a/fs/fsopen.c b/fs/fsopen.c
new file mode 100644
index 0000000000000000000000000000000000000000..d256f1ac9ff1bf1158b483b7c7efc85abc55a367
--- /dev/null
+++ b/fs/fsopen.c
@@ -0,0 +1,88 @@
+/* Filesystem access-by-fd.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/fs_context.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/security.h>
+#include <linux/anon_inodes.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <uapi/linux/mount.h>
+#include "mount.h"
+
+static int fscontext_release(struct inode *inode, struct file *file)
+{
+ struct fs_context *fc = file->private_data;
+
+ if (fc) {
+ file->private_data = NULL;
+ put_fs_context(fc);
+ }
+ return 0;
+}
+
+const struct file_operations fscontext_fops = {
+ .release = fscontext_release,
+ .llseek = no_llseek,
+};
+
+/*
+ * Attach a filesystem context to a file and an fd.
+ */
+static int fscontext_create_fd(struct fs_context *fc, unsigned int o_flags)
+{
+ int fd;
+
+ fd = anon_inode_getfd("fscontext", &fscontext_fops, fc,
+ O_RDWR | o_flags);
+ if (fd < 0)
+ put_fs_context(fc);
+ return fd;
+}
+
+/*
+ * Open a filesystem by name so that it can be configured for mounting.
+ *
+ * We are allowed to specify a container in which the filesystem will be
+ * opened, thereby indicating which namespaces will be used (notably, which
+ * network namespace will be used for network filesystems).
+ */
+SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags)
+{
+ struct file_system_type *fs_type;
+ struct fs_context *fc;
+ const char *fs_name;
+
+ if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (flags & ~FSOPEN_CLOEXEC)
+ return -EINVAL;
+
+ fs_name = strndup_user(_fs_name, PAGE_SIZE);
+ if (IS_ERR(fs_name))
+ return PTR_ERR(fs_name);
+
+ fs_type = get_fs_type(fs_name);
+ kfree(fs_name);
+ if (!fs_type)
+ return -ENODEV;
+
+ fc = fs_context_for_mount(fs_type, 0);
+ put_filesystem(fs_type);
+ if (IS_ERR(fc))
+ return PTR_ERR(fc);
+
+ fc->phase = FS_CONTEXT_CREATE_PARAMS;
+ return fscontext_create_fd(fc, flags & FSOPEN_CLOEXEC ? O_CLOEXEC : 0);
+}
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index eaca452088fa53034b0e64335e7b72719294e9ac..7ab8b44fab3ef551581d5649ea96c2952caed839 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -15,6 +15,7 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/security.h>
+#include <linux/mutex.h>
struct cred;
struct dentry;
@@ -34,6 +35,19 @@ enum fs_context_purpose {
FS_CONTEXT_FOR_RECONFIGURE, /* Superblock reconfiguration (remount) */
};
+/*
+ * Userspace usage phase for fsopen/fspick.
+ */
+enum fs_context_phase {
+ FS_CONTEXT_CREATE_PARAMS, /* Loading params for sb creation */
+ FS_CONTEXT_CREATING, /* A superblock is being created */
+ FS_CONTEXT_AWAITING_MOUNT, /* Superblock created, awaiting fsmount() */
+ FS_CONTEXT_AWAITING_RECONF, /* Awaiting initialisation for reconfiguration */
+ FS_CONTEXT_RECONF_PARAMS, /* Loading params for reconfiguration */
+ FS_CONTEXT_RECONFIGURING, /* Reconfiguring the superblock */
+ FS_CONTEXT_FAILED, /* Failed to correctly transition a context */
+};
+
/*
* Type of parameter value.
*/
@@ -74,6 +88,7 @@ struct fs_parameter {
*/
struct fs_context {
const struct fs_context_operations *ops;
+ struct mutex uapi_mutex; /* Userspace access mutex */
struct file_system_type *fs_type;
void *fs_private; /* The filesystem's context */
struct dentry *root; /* The root and superblock */
@@ -88,6 +103,7 @@ struct fs_context {
unsigned int sb_flags_mask; /* Superblock flags that were changed */
unsigned int lsm_flags; /* Information flags from the fs to the LSM */
enum fs_context_purpose purpose:8;
+ enum fs_context_phase phase:8; /* The phase the context is in */
bool need_free:1; /* Need to call ops->free() */
bool global:1; /* Goes into &init_user_ns */
};
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 84347fc0a1a71567cbd750e409e7dabb3a9438de..0c9bd5427e8f583323a71e267969533e55764589 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -989,6 +989,7 @@ asmlinkage long sys_open_tree(int dfd, const char __user *path, unsigned flags);
asmlinkage long sys_move_mount(int from_dfd, const char __user *from_path,
int to_dfd, const char __user *to_path,
unsigned int ms_flags);
+asmlinkage long sys_fsopen(const char __user *fs_name, unsigned int flags);
asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
siginfo_t __user *info,
unsigned int flags);
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 3634e065836cb99e6c38b029d15d77c4ef10d602..7570df43d08fdfc097a011e9b67f09f48698987d 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -72,4 +72,9 @@
#define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */
#define MOVE_MOUNT__MASK 0x00000077
+/*
+ * fsopen() flags.
+ */
+#define FSOPEN_CLOEXEC 0x00000001
+
#endif /* _UAPI_LINUX_MOUNT_H */