Commit becfd1f3 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Al Viro

vfs: Add open by file handle support

[AV: duplicate of open() guts removed; file_open_root() used instead]
Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 990d6c2d
......@@ -2284,3 +2284,16 @@ asmlinkage long compat_sys_timerfd_gettime(int ufd,
}
#endif /* CONFIG_TIMERFD */
#ifdef CONFIG_FHANDLE
/*
* Exactly like fs/open.c:sys_open_by_handle_at(), except that it
* doesn't set the O_LARGEFILE flag.
*/
asmlinkage long
compat_sys_open_by_handle_at(int mountdirfd,
struct file_handle __user *handle, int flags)
{
return do_handle_open(mountdirfd, handle, flags);
}
#endif
......@@ -374,6 +374,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
/*
* Try to get any dentry for the given file handle from the filesystem.
*/
if (!nop || !nop->fh_to_dentry)
return ERR_PTR(-ESTALE);
result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
if (!result)
result = ERR_PTR(-ESTALE);
......
......@@ -5,6 +5,8 @@
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/fs_struct.h>
#include <linux/fsnotify.h>
#include <asm/uaccess.h>
#include "internal.h"
......@@ -105,3 +107,159 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
}
return err;
}
static struct vfsmount *get_vfsmount_from_fd(int fd)
{
struct path path;
if (fd == AT_FDCWD) {
struct fs_struct *fs = current->fs;
spin_lock(&fs->lock);
path = fs->pwd;
mntget(path.mnt);
spin_unlock(&fs->lock);
} else {
int fput_needed;
struct file *file = fget_light(fd, &fput_needed);
if (!file)
return ERR_PTR(-EBADF);
path = file->f_path;
mntget(path.mnt);
fput_light(file, fput_needed);
}
return path.mnt;
}
static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
{
return 1;
}
static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
struct path *path)
{
int retval = 0;
int handle_dwords;
path->mnt = get_vfsmount_from_fd(mountdirfd);
if (IS_ERR(path->mnt)) {
retval = PTR_ERR(path->mnt);
goto out_err;
}
/* change the handle size to multiple of sizeof(u32) */
handle_dwords = handle->handle_bytes >> 2;
path->dentry = exportfs_decode_fh(path->mnt,
(struct fid *)handle->f_handle,
handle_dwords, handle->handle_type,
vfs_dentry_acceptable, NULL);
if (IS_ERR(path->dentry)) {
retval = PTR_ERR(path->dentry);
goto out_mnt;
}
return 0;
out_mnt:
mntput(path->mnt);
out_err:
return retval;
}
static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
struct path *path)
{
int retval = 0;
struct file_handle f_handle;
struct file_handle *handle = NULL;
/*
* With handle we don't look at the execute bit on the
* the directory. Ideally we would like CAP_DAC_SEARCH.
* But we don't have that
*/
if (!capable(CAP_DAC_READ_SEARCH)) {
retval = -EPERM;
goto out_err;
}
if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
retval = -EFAULT;
goto out_err;
}
if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
(f_handle.handle_bytes == 0)) {
retval = -EINVAL;
goto out_err;
}
handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
GFP_KERNEL);
if (!handle) {
retval = -ENOMEM;
goto out_err;
}
/* copy the full handle */
if (copy_from_user(handle, ufh,
sizeof(struct file_handle) +
f_handle.handle_bytes)) {
retval = -EFAULT;
goto out_handle;
}
retval = do_handle_to_path(mountdirfd, handle, path);
out_handle:
kfree(handle);
out_err:
return retval;
}
long do_handle_open(int mountdirfd,
struct file_handle __user *ufh, int open_flag)
{
long retval = 0;
struct path path;
struct file *file;
int fd;
retval = handle_to_path(mountdirfd, ufh, &path);
if (retval)
return retval;
fd = get_unused_fd_flags(open_flag);
if (fd < 0) {
path_put(&path);
return fd;
}
file = file_open_root(path.dentry, path.mnt, "", open_flag);
if (IS_ERR(file)) {
put_unused_fd(fd);
retval = PTR_ERR(file);
} else {
retval = fd;
fsnotify_open(file);
fd_install(fd, file);
}
path_put(&path);
return retval;
}
/**
* sys_open_by_handle_at: Open the file handle
* @mountdirfd: directory file descriptor
* @handle: file handle to be opened
* @flag: open flags.
*
* @mountdirfd indicate the directory file descriptor
* of the mount point. file handle is decoded relative
* to the vfsmount pointed by the @mountdirfd. @flags
* value is same as the open(2) flags.
*/
SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
struct file_handle __user *, handle,
int, flags)
{
long ret;
if (force_o_largefile())
flags |= O_LARGEFILE;
ret = do_handle_open(mountdirfd, handle, flags);
return ret;
}
......@@ -117,6 +117,9 @@ extern struct file *do_filp_open(int dfd, const char *pathname,
extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
const char *, const struct open_flags *, int lookup_flags);
extern long do_handle_open(int mountdirfd,
struct file_handle __user *ufh, int open_flag);
/*
* inode.c
*/
......
......@@ -836,4 +836,7 @@ asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
struct file_handle __user *handle,
int __user *mnt_id, int flag);
asmlinkage long sys_open_by_handle_at(int mountdirfd,
struct file_handle __user *handle,
int flags);
#endif
......@@ -189,3 +189,5 @@ cond_syscall(sys_fanotify_mark);
/* open by handle */
cond_syscall(sys_name_to_handle_at);
cond_syscall(sys_open_by_handle_at);
cond_syscall(compat_sys_open_by_handle_at);
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