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authorAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>2011-01-29 08:13:26 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-15 02:21:44 -0400
commitbecfd1f37544798cbdfd788f32c827160fab98c1 (patch)
tree80353bdc7e59c661e841d2d0029bb308c0ed4da0
parent990d6c2d7aee921e3bce22b2d6a750fd552262be (diff)
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>
-rw-r--r--fs/compat.c13
-rw-r--r--fs/exportfs/expfs.c2
-rw-r--r--fs/fhandle.c158
-rw-r--r--fs/internal.h3
-rw-r--r--include/linux/syscalls.h3
-rw-r--r--kernel/sys_ni.c2
6 files changed, 181 insertions, 0 deletions
diff --git a/fs/compat.c b/fs/compat.c
index a071775f3bb3..c6d31a3bab88 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -2284,3 +2284,16 @@ asmlinkage long compat_sys_timerfd_gettime(int ufd,
2284} 2284}
2285 2285
2286#endif /* CONFIG_TIMERFD */ 2286#endif /* CONFIG_TIMERFD */
2287
2288#ifdef CONFIG_FHANDLE
2289/*
2290 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
2291 * doesn't set the O_LARGEFILE flag.
2292 */
2293asmlinkage long
2294compat_sys_open_by_handle_at(int mountdirfd,
2295 struct file_handle __user *handle, int flags)
2296{
2297 return do_handle_open(mountdirfd, handle, flags);
2298}
2299#endif
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index cfe55731b6dc..b05acb796135 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -374,6 +374,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
374 /* 374 /*
375 * Try to get any dentry for the given file handle from the filesystem. 375 * Try to get any dentry for the given file handle from the filesystem.
376 */ 376 */
377 if (!nop || !nop->fh_to_dentry)
378 return ERR_PTR(-ESTALE);
377 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); 379 result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
378 if (!result) 380 if (!result)
379 result = ERR_PTR(-ESTALE); 381 result = ERR_PTR(-ESTALE);
diff --git a/fs/fhandle.c b/fs/fhandle.c
index 9f79e743a840..bf93ad2bee07 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -5,6 +5,8 @@
5#include <linux/mount.h> 5#include <linux/mount.h>
6#include <linux/namei.h> 6#include <linux/namei.h>
7#include <linux/exportfs.h> 7#include <linux/exportfs.h>
8#include <linux/fs_struct.h>
9#include <linux/fsnotify.h>
8#include <asm/uaccess.h> 10#include <asm/uaccess.h>
9#include "internal.h" 11#include "internal.h"
10 12
@@ -105,3 +107,159 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
105 } 107 }
106 return err; 108 return err;
107} 109}
110
111static struct vfsmount *get_vfsmount_from_fd(int fd)
112{
113 struct path path;
114
115 if (fd == AT_FDCWD) {
116 struct fs_struct *fs = current->fs;
117 spin_lock(&fs->lock);
118 path = fs->pwd;
119 mntget(path.mnt);
120 spin_unlock(&fs->lock);
121 } else {
122 int fput_needed;
123 struct file *file = fget_light(fd, &fput_needed);
124 if (!file)
125 return ERR_PTR(-EBADF);
126 path = file->f_path;
127 mntget(path.mnt);
128 fput_light(file, fput_needed);
129 }
130 return path.mnt;
131}
132
133static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
134{
135 return 1;
136}
137
138static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
139 struct path *path)
140{
141 int retval = 0;
142 int handle_dwords;
143
144 path->mnt = get_vfsmount_from_fd(mountdirfd);
145 if (IS_ERR(path->mnt)) {
146 retval = PTR_ERR(path->mnt);
147 goto out_err;
148 }
149 /* change the handle size to multiple of sizeof(u32) */
150 handle_dwords = handle->handle_bytes >> 2;
151 path->dentry = exportfs_decode_fh(path->mnt,
152 (struct fid *)handle->f_handle,
153 handle_dwords, handle->handle_type,
154 vfs_dentry_acceptable, NULL);
155 if (IS_ERR(path->dentry)) {
156 retval = PTR_ERR(path->dentry);
157 goto out_mnt;
158 }
159 return 0;
160out_mnt:
161 mntput(path->mnt);
162out_err:
163 return retval;
164}
165
166static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
167 struct path *path)
168{
169 int retval = 0;
170 struct file_handle f_handle;
171 struct file_handle *handle = NULL;
172
173 /*
174 * With handle we don't look at the execute bit on the
175 * the directory. Ideally we would like CAP_DAC_SEARCH.
176 * But we don't have that
177 */
178 if (!capable(CAP_DAC_READ_SEARCH)) {
179 retval = -EPERM;
180 goto out_err;
181 }
182 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
183 retval = -EFAULT;
184 goto out_err;
185 }
186 if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
187 (f_handle.handle_bytes == 0)) {
188 retval = -EINVAL;
189 goto out_err;
190 }
191 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
192 GFP_KERNEL);
193 if (!handle) {
194 retval = -ENOMEM;
195 goto out_err;
196 }
197 /* copy the full handle */
198 if (copy_from_user(handle, ufh,
199 sizeof(struct file_handle) +
200 f_handle.handle_bytes)) {
201 retval = -EFAULT;
202 goto out_handle;
203 }
204
205 retval = do_handle_to_path(mountdirfd, handle, path);
206
207out_handle:
208 kfree(handle);
209out_err:
210 return retval;
211}
212
213long do_handle_open(int mountdirfd,
214 struct file_handle __user *ufh, int open_flag)
215{
216 long retval = 0;
217 struct path path;
218 struct file *file;
219 int fd;
220
221 retval = handle_to_path(mountdirfd, ufh, &path);
222 if (retval)
223 return retval;
224
225 fd = get_unused_fd_flags(open_flag);
226 if (fd < 0) {
227 path_put(&path);
228 return fd;
229 }
230 file = file_open_root(path.dentry, path.mnt, "", open_flag);
231 if (IS_ERR(file)) {
232 put_unused_fd(fd);
233 retval = PTR_ERR(file);
234 } else {
235 retval = fd;
236 fsnotify_open(file);
237 fd_install(fd, file);
238 }
239 path_put(&path);
240 return retval;
241}
242
243/**
244 * sys_open_by_handle_at: Open the file handle
245 * @mountdirfd: directory file descriptor
246 * @handle: file handle to be opened
247 * @flag: open flags.
248 *
249 * @mountdirfd indicate the directory file descriptor
250 * of the mount point. file handle is decoded relative
251 * to the vfsmount pointed by the @mountdirfd. @flags
252 * value is same as the open(2) flags.
253 */
254SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
255 struct file_handle __user *, handle,
256 int, flags)
257{
258 long ret;
259
260 if (force_o_largefile())
261 flags |= O_LARGEFILE;
262
263 ret = do_handle_open(mountdirfd, handle, flags);
264 return ret;
265}
diff --git a/fs/internal.h b/fs/internal.h
index 52abc5287f50..f3d15de44b15 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -117,6 +117,9 @@ extern struct file *do_filp_open(int dfd, const char *pathname,
117extern struct file *do_file_open_root(struct dentry *, struct vfsmount *, 117extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
118 const char *, const struct open_flags *, int lookup_flags); 118 const char *, const struct open_flags *, int lookup_flags);
119 119
120extern long do_handle_open(int mountdirfd,
121 struct file_handle __user *ufh, int open_flag);
122
120/* 123/*
121 * inode.c 124 * inode.c
122 */ 125 */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 970112613fb4..2d9b79c0f224 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -836,4 +836,7 @@ asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
836asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name, 836asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,
837 struct file_handle __user *handle, 837 struct file_handle __user *handle,
838 int __user *mnt_id, int flag); 838 int __user *mnt_id, int flag);
839asmlinkage long sys_open_by_handle_at(int mountdirfd,
840 struct file_handle __user *handle,
841 int flags);
839#endif 842#endif
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 4e013439ac28..25cc41cd8f33 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -189,3 +189,5 @@ cond_syscall(sys_fanotify_mark);
189 189
190/* open by handle */ 190/* open by handle */
191cond_syscall(sys_name_to_handle_at); 191cond_syscall(sys_name_to_handle_at);
192cond_syscall(sys_open_by_handle_at);
193cond_syscall(compat_sys_open_by_handle_at);