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Subject[PATCH -V10 3/9] vfs: Add open by file handle support
Date
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/exportfs/expfs.c | 2 +
fs/namei.c | 50 +++++++++++++
fs/open.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 3 +-
include/linux/syscalls.h | 2 +
5 files changed, 233 insertions(+), 1 deletions(-)
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index d103c31..e73c0ab 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -373,6 +373,8 @@ 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);
diff --git a/fs/namei.c b/fs/namei.c
index b86b96f..21cf0a5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1556,6 +1556,56 @@ static int open_will_truncate(int flag, struct inode *inode)
return (flag & O_TRUNC);
}

+struct file *finish_open_handle(struct path *path,
+ int open_flag, int acc_mode)
+{
+ int error;
+ struct file *filp;
+ int will_truncate;
+
+ will_truncate = open_will_truncate(open_flag, path->dentry->d_inode);
+ if (will_truncate) {
+ error = mnt_want_write(path->mnt);
+ if (error)
+ goto exit;
+ }
+ error = may_open(path, acc_mode, open_flag);
+ if (error) {
+ if (will_truncate)
+ mnt_drop_write(path->mnt);
+ goto exit;
+ }
+ filp = dentry_open(path->dentry, path->mnt, open_flag, current_cred());
+ if (!IS_ERR(filp)) {
+ error = ima_file_check(filp, acc_mode);
+ if (error) {
+ fput(filp);
+ filp = ERR_PTR(error);
+ }
+ }
+ if (!IS_ERR(filp)) {
+ if (will_truncate) {
+ error = handle_truncate(path);
+ if (error) {
+ fput(filp);
+ filp = ERR_PTR(error);
+ }
+ }
+ }
+ /*
+ * It is now safe to drop the mnt write
+ * because the filp has had a write taken
+ * on its behalf.
+ */
+ if (will_truncate)
+ mnt_drop_write(path->mnt);
+ return filp;
+
+exit:
+ path_put(path);
+ return ERR_PTR(error);
+}
+
static struct file *finish_open(struct nameidata *nd,
int open_flag, int acc_mode)
{
diff --git a/fs/open.c b/fs/open.c
index 9dbd317..bb28c38 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1303,3 +1303,180 @@ SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name,
return -ENOSYS;
}
#endif
+
+#ifdef CONFIG_EXPORTFS
+static struct vfsmount *get_vfsmount_from_fd(int fd)
+{
+ int fput_needed;
+ struct path *path;
+ struct file *filep;
+
+ if (fd == AT_FDCWD) {
+ struct fs_struct *fs = current->fs;
+ read_lock(&fs->lock);
+ path = &fs->pwd;
+ mntget(path->mnt);
+ read_unlock(&fs->lock);
+ } else {
+ filep = fget_light(fd, &fput_needed);
+ if (!filep)
+ return ERR_PTR(-EBADF);
+ path = &filep->f_path;
+ mntget(path->mnt);
+ fput_light(filep, fput_needed);
+ }
+ return path->mnt;
+}
+
+static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
+{
+ return 1;
+}
+
+static struct path *handle_to_path(int mountdirfd, struct file_handle *handle)
+{
+ int retval;
+ int handle_size;
+ struct path *path;
+
+ path = kmalloc(sizeof(struct path), GFP_KERNEL);
+ if (!path)
+ return ERR_PTR(-ENOMEM);
+
+ 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_size = handle->handle_size >> 2;
+ path->dentry = exportfs_decode_fh(path->mnt,
+ (struct fid *)handle->f_handle,
+ handle_size, handle->handle_type,
+ vfs_dentry_acceptable, NULL);
+ if (IS_ERR(path->dentry)) {
+ retval = PTR_ERR(path->dentry);
+ goto out_mnt;
+ }
+ return path;
+out_mnt:
+ mntput(path->mnt);
+out_err:
+ kfree(path);
+ return ERR_PTR(retval);
+}
+
+static long do_sys_open_by_handle(int mountdirfd,
+ struct file_handle __user *ufh, int open_flag)
+{
+ int acc_mode;
+ int fd, retval = 0;
+ struct file *filp;
+ struct path *path;
+ struct file_handle f_handle;
+ struct file_handle *handle = NULL;
+
+ /* can't use O_CREATE with open_by_handle */
+ if (open_flag & O_CREAT) {
+ retval = -EINVAL;
+ goto out_err;
+ }
+ if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
+ retval = -EFAULT;
+ goto out_err;
+ }
+ if ((f_handle.handle_size > MAX_HANDLE_SZ) ||
+ (f_handle.handle_size <= 0)) {
+ retval = -EINVAL;
+ goto out_err;
+ }
+ if (!capable(CAP_DAC_OVERRIDE)) {
+ retval = -EPERM;
+ goto out_err;
+ }
+ handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size,
+ 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_size)) {
+ retval = -EFAULT;
+ goto out_handle;
+ }
+ path = handle_to_path(mountdirfd, handle);
+ if (IS_ERR(path)) {
+ retval = PTR_ERR(path);
+ goto out_handle;
+ }
+ /*
+ * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
+ * check for O_DSYNC if the need any syncing at all we enforce it's
+ * always set instead of having to deal with possibly weird behaviour
+ * for malicious applications setting only __O_SYNC.
+ */
+ if (open_flag & __O_SYNC)
+ open_flag |= O_DSYNC;
+
+ acc_mode = MAY_OPEN | ACC_MODE(open_flag);
+
+ /* O_TRUNC implies we need access checks for write permissions */
+ if (open_flag & O_TRUNC)
+ acc_mode |= MAY_WRITE;
+ /*
+ * Allow the LSM permission hook to distinguish append
+ * access from general write access.
+ */
+ if (open_flag & O_APPEND)
+ acc_mode |= MAY_APPEND;
+
+ fd = get_unused_fd_flags(open_flag);
+ if (fd < 0) {
+ retval = fd;
+ goto out_path;
+ }
+ filp = finish_open_handle(path, open_flag, acc_mode);
+ if (IS_ERR(filp)) {
+ put_unused_fd(fd);
+ retval = PTR_ERR(filp);
+ } else {
+ retval = fd;
+ fsnotify_open(filp->f_path.dentry);
+ fd_install(fd, filp);
+ }
+ kfree(path);
+ kfree(handle);
+ return retval;
+
+out_path:
+ path_put(path);
+ kfree(path);
+out_handle:
+ kfree(handle);
+out_err:
+ return retval;
+}
+
+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_sys_open_by_handle(mountdirfd, handle, flags);
+ return ret;
+}
+#else
+SYSCALL_DEFINE3(open_by_handle, int, mountdirfd,
+ struct file_handle __user *, handle,
+ int, flags)
+{
+ return -ENOSYS;
+}
+#endif
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d428b1a..c30940c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2140,7 +2140,8 @@ extern int may_open(struct path *, int, int);

extern int kernel_read(struct file *, loff_t, char *, unsigned long);
extern struct file * open_exec(const char *);
-
+extern struct file *finish_open_handle(struct path *, int, int);
+
/* fs/dcache.c -- generic fs support functions */
extern int is_subdir(struct dentry *, struct dentry *);
extern int path_is_under(struct path *, struct path *);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index d0deef0..58b9702 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -849,5 +849,7 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len,
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 flag);
+asmlinkage long sys_open_by_handle_at(int mountdirfd,
+ struct file_handle __user *handle, int flags);

#endif
--
1.7.1.78.g212f0


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