lkml.org 
[lkml]   [2017]   [Oct]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Subject[PATCH 06/14] VFS: Implement fsmount() to effect a pre-configured mount [ver #6]
    From
    Date
    Provide a system call by which a filesystem opened with fsopen() and
    configured by a series of writes can be mounted:

    int ret = fsmount(int fsfd, int dfd, const char *path,
    unsigned int at_flags, unsigned int flags);

    where fsfd is the fd returned by fsopen(), dfd, path and at_flags locate
    the mountpoint and flags are the applicable MS_* flags. dfd can be
    AT_FDCWD or an fd open to a directory.

    In the event that fsmount() fails, it may be possible to get an error
    message by calling read(). If no message is available, ENODATA will be
    reported.

    Signed-off-by: David Howells <dhowells@redhat.com>
    ---

    arch/x86/entry/syscalls/syscall_32.tbl | 1
    arch/x86/entry/syscalls/syscall_64.tbl | 1
    fs/namespace.c | 82 ++++++++++++++++++++++++++++++++
    include/linux/syscalls.h | 2 +
    kernel/sys_ni.c | 1
    5 files changed, 87 insertions(+)

    diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
    index 9bf8d4c62f85..abe6ea95e0e6 100644
    --- a/arch/x86/entry/syscalls/syscall_32.tbl
    +++ b/arch/x86/entry/syscalls/syscall_32.tbl
    @@ -392,3 +392,4 @@
    383 i386 statx sys_statx
    384 i386 arch_prctl sys_arch_prctl compat_sys_arch_prctl
    385 i386 fsopen sys_fsopen
    +386 i386 fsmount sys_fsmount
    diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
    index 9b198c5fc412..0977c5079831 100644
    --- a/arch/x86/entry/syscalls/syscall_64.tbl
    +++ b/arch/x86/entry/syscalls/syscall_64.tbl
    @@ -340,6 +340,7 @@
    331 common pkey_free sys_pkey_free
    332 common statx sys_statx
    333 common fsopen sys_fsopen
    +334 common fsmount sys_fsmount

    #
    # x32-specific system call numbers start at 512 to avoid cache impact
    diff --git a/fs/namespace.c b/fs/namespace.c
    index d6b0b0067f6d..8676658b6b2c 100644
    --- a/fs/namespace.c
    +++ b/fs/namespace.c
    @@ -3188,6 +3188,88 @@ struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
    EXPORT_SYMBOL_GPL(kern_mount_data);

    /*
    + * Mount a new, prepared superblock (specified by fs_fd) on the location
    + * specified by dfd and dir_name. dfd can be AT_FDCWD, a dir fd or a container
    + * fd. This cannot be used for binding, moving or remounting mounts.
    + */
    +SYSCALL_DEFINE5(fsmount, int, fs_fd, int, dfd, const char __user *, dir_name,
    + unsigned int, at_flags, unsigned int, flags)
    +{
    + struct fs_context *fc;
    + struct path mountpoint;
    + struct fd f;
    + unsigned int lookup_flags, mnt_flags = 0;
    + long ret;
    +
    + if ((at_flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
    + AT_EMPTY_PATH)) != 0)
    + return -EINVAL;
    +
    + if (flags & ~(MS_RDONLY | MS_NOSUID | MS_NODEV | MS_NOEXEC |
    + MS_NOATIME | MS_NODIRATIME | MS_RELATIME | MS_STRICTATIME))
    + return -EINVAL;
    +
    + if (flags & MS_RDONLY)
    + mnt_flags |= MNT_READONLY;
    + if (flags & MS_NOSUID)
    + mnt_flags |= MNT_NOSUID;
    + if (flags & MS_NODEV)
    + mnt_flags |= MNT_NODEV;
    + if (flags & MS_NOEXEC)
    + mnt_flags |= MNT_NOEXEC;
    + if (flags & MS_NODIRATIME)
    + mnt_flags |= MNT_NODIRATIME;
    +
    + if (flags & MS_STRICTATIME) {
    + if (flags & MS_NOATIME)
    + return -EINVAL;
    + } else if (flags & MS_NOATIME) {
    + mnt_flags |= MNT_NOATIME;
    + } else {
    + mnt_flags |= MNT_RELATIME;
    + }
    +
    + f = fdget(fs_fd);
    + if (!f.file)
    + return -EBADF;
    +
    + ret = -EINVAL;
    + if (f.file->f_op != &fs_fs_fops)
    + goto err_fsfd;
    +
    + fc = f.file->private_data;
    +
    + ret = -EPERM;
    + if (!may_mount() ||
    + ((fc->sb_flags & MS_MANDLOCK) && !may_mandlock()))
    + goto err_fsfd;
    +
    + /* There must be a valid superblock or we can't mount it */
    + ret = -EINVAL;
    + if (!fc->root)
    + goto err_fsfd;
    +
    + /* Find the mountpoint. A container can be specified in dfd. */
    + lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
    + if (at_flags & AT_SYMLINK_NOFOLLOW)
    + lookup_flags &= ~LOOKUP_FOLLOW;
    + if (at_flags & AT_NO_AUTOMOUNT)
    + lookup_flags &= ~LOOKUP_AUTOMOUNT;
    + if (at_flags & AT_EMPTY_PATH)
    + lookup_flags |= LOOKUP_EMPTY;
    + ret = user_path_at(dfd, dir_name, lookup_flags, &mountpoint);
    + if (ret < 0)
    + goto err_fsfd;
    +
    + ret = do_new_mount_fc(fc, &mountpoint, mnt_flags);
    +
    + path_put(&mountpoint);
    +err_fsfd:
    + fdput(f);
    + return ret;
    +}
    +
    +/*
    * Return true if path is reachable from root
    *
    * namespace_sem or mount_lock is held
    diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
    index 7cd1b65a4152..e82dde171ce8 100644
    --- a/include/linux/syscalls.h
    +++ b/include/linux/syscalls.h
    @@ -942,5 +942,7 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags,
    unsigned mask, struct statx __user *buffer);
    asmlinkage long sys_fsopen(const char *fs_name, unsigned int flags,
    void *reserved3, void *reserved4, void *reserved5);
    +asmlinkage long sys_fsmount(int fsfd, int dfd, const char *path, unsigned int at_flags,
    + unsigned int flags);

    #endif
    diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
    index de1dc63e7e47..a0fe764bd5dd 100644
    --- a/kernel/sys_ni.c
    +++ b/kernel/sys_ni.c
    @@ -261,3 +261,4 @@ cond_syscall(sys_pkey_free);

    /* fd-based mount */
    cond_syscall(sys_fsopen);
    +cond_syscall(sys_fsmount);
    \
     
     \ /
      Last update: 2017-10-06 17:55    [W:3.150 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site