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vfs: Add open by file handle support

[AV: duplicate of open() guts removed; file_open_root() used instead]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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1 parent 990d6c2 commit becfd1f37544798cbdfd788f32c827160fab98c1 @kvaneesh kvaneesh committed with Al Viro Jan 29, 2011
Showing with 181 additions and 0 deletions.
  1. +13 −0 fs/compat.c
  2. +2 −0 fs/exportfs/expfs.c
  3. +158 −0 fs/fhandle.c
  4. +3 −0 fs/internal.h
  5. +3 −0 include/linux/syscalls.h
  6. +2 −0 kernel/sys_ni.c
View
@@ -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
View
@@ -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);
View
@@ -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;
+}
View
@@ -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
View
@@ -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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