vmsplice(): lift importing iovec into vmsplice(2) and compat counterpart

... getting rid of transformations in the latter - just use
compat_import_iovec().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 75 insertions, 69 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 005d09cf3fa8..e3d0ae5383e7 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1242,38 +1242,26 @@ static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
  * For lack of a better implementation, implement vmsplice() to userspace
  * as a simple copy of the pipes pages to the user iov.
  */
-static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
-                             unsigned long nr_segs, unsigned int flags)
+static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
+                             unsigned int flags)
 {
-        struct pipe_inode_info *pipe;
-        struct splice_desc sd;
-        long ret;
-        struct iovec iovstack[UIO_FASTIOV];
-        struct iovec *iov = iovstack;
-        struct iov_iter iter;
+        struct pipe_inode_info *pipe = get_pipe_info(file);
+        struct splice_desc sd = {
+                .total_len = iov_iter_count(iter),
+                .flags = flags,
+                .u.data = iter
+        };
+        long ret = 0;
 
-        pipe = get_pipe_info(file);
         if (!pipe)
                 return -EBADF;
 
-        ret = import_iovec(READ, uiov, nr_segs,
-                           ARRAY_SIZE(iovstack), &iov, &iter);
-        if (ret < 0)
-                return ret;
-
-        sd.total_len = iov_iter_count(&iter);
-        sd.len = 0;
-        sd.flags = flags;
-        sd.u.data = &iter;
-        sd.pos = 0;
-
         if (sd.total_len) {
                 pipe_lock(pipe);
                 ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
                 pipe_unlock(pipe);
         }
 
-        kfree(iov);
         return ret;
 }
 
@@ -1282,14 +1270,11 @@ static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
  * as splice-from-memory, where the regular splice is splice-from-file (or
  * to file). In both cases the output is a pipe, naturally.
  */
-static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
-                             unsigned long nr_segs, unsigned int flags)
+static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
+                             unsigned int flags)
 {
         struct pipe_inode_info *pipe;
-        struct iovec iovstack[UIO_FASTIOV];
-        struct iovec *iov = iovstack;
-        struct iov_iter from;
-        long ret;
+        long ret = 0;
         unsigned buf_flag = 0;
 
         if (flags & SPLICE_F_GIFT)
@@ -1299,22 +1284,31 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
         if (!pipe)
                 return -EBADF;
 
-        ret = import_iovec(WRITE, uiov, nr_segs,
-                           ARRAY_SIZE(iovstack), &iov, &from);
-        if (ret < 0)
-                return ret;
-
         pipe_lock(pipe);
         ret = wait_for_space(pipe, flags);
         if (!ret)
-                ret = iter_to_pipe(&from, pipe, buf_flag);
+                ret = iter_to_pipe(iter, pipe, buf_flag);
         pipe_unlock(pipe);
         if (ret > 0)
                 wakeup_pipe_readers(pipe);
-        kfree(iov);
         return ret;
 }
 
+static int vmsplice_type(struct fd f, int *type)
+{
+        if (!f.file)
+                return -EBADF;
+        if (f.file->f_mode & FMODE_WRITE) {
+                *type = WRITE;
+        } else if (f.file->f_mode & FMODE_READ) {
+                *type = READ;
+        } else {
+                fdput(f);
+                return -EBADF;
+        }
+        return 0;
+}
+
 /*
  * Note that vmsplice only really supports true splicing _from_ user memory
  * to a pipe, not the other way around. Splicing from user memory is a simple
@@ -1331,57 +1325,69 @@ static long vmsplice_to_pipe(struct file *file, const struct iovec __user *uiov,
  * Currently we punt and implement it as a normal copy, see pipe_to_user().
  *
  */
-static long do_vmsplice(int fd, const struct iovec __user *iov,
-                        unsigned long nr_segs, unsigned int flags)
+static long do_vmsplice(struct file *f, struct iov_iter *iter, unsigned int flags)
 {
-        struct fd f;
-        long error;
-
         if (unlikely(flags & ~SPLICE_F_ALL))
                 return -EINVAL;
-        if (unlikely(nr_segs > UIO_MAXIOV))
-                return -EINVAL;
-        else if (unlikely(!nr_segs))
-                return 0;
 
-        error = -EBADF;
-        f = fdget(fd);
-        if (f.file) {
-                if (f.file->f_mode & FMODE_WRITE)
-                        error = vmsplice_to_pipe(f.file, iov, nr_segs, flags);
-                else if (f.file->f_mode & FMODE_READ)
-                        error = vmsplice_to_user(f.file, iov, nr_segs, flags);
-
-                fdput(f);
-        }
+        if (!iov_iter_count(iter))
+                return 0;
 
-        return error;
+        if (iov_iter_rw(iter) == WRITE)
+                return vmsplice_to_pipe(f, iter, flags);
+        else
+                return vmsplice_to_user(f, iter, flags);
 }
 
-SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
+SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, uiov,
                 unsigned long, nr_segs, unsigned int, flags)
 {
-        return do_vmsplice(fd, iov, nr_segs, flags);
+        struct iovec iovstack[UIO_FASTIOV];
+        struct iovec *iov = iovstack;
+        struct iov_iter iter;
+        long error;
+        struct fd f;
+        int type;
+
+        f = fdget(fd);
+        error = vmsplice_type(f, &type);
+        if (error)
+                return error;
+
+        error = import_iovec(type, uiov, nr_segs,
+                             ARRAY_SIZE(iovstack), &iov, &iter);
+        if (!error) {
+                error = do_vmsplice(f.file, &iter, flags);
+                kfree(iov);
+        }
+        fdput(f);
+        return error;
 }
 
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE4(vmsplice, int, fd, const struct compat_iovec __user *, iov32,
                     unsigned int, nr_segs, unsigned int, flags)
 {
-        unsigned i;
-        struct iovec __user *iov;
-        if (nr_segs > UIO_MAXIOV)
-                return -EINVAL;
-        iov = compat_alloc_user_space(nr_segs * sizeof(struct iovec));
-        for (i = 0; i < nr_segs; i++) {
-                struct compat_iovec v;
-                if (get_user(v.iov_base, &iov32[i].iov_base) ||
-                    get_user(v.iov_len, &iov32[i].iov_len) ||
-                    put_user(compat_ptr(v.iov_base), &iov[i].iov_base) ||
-                    put_user(v.iov_len, &iov[i].iov_len))
-                        return -EFAULT;
+        struct iovec iovstack[UIO_FASTIOV];
+        struct iovec *iov = iovstack;
+        struct iov_iter iter;
+        long error;
+        struct fd f;
+        int type;
+
+        f = fdget(fd);
+        error = vmsplice_type(f, &type);
+        if (error)
+                return error;
+
+        error = compat_import_iovec(type, iov32, nr_segs,
+                             ARRAY_SIZE(iovstack), &iov, &iter);
+        if (!error) {
+                error = do_vmsplice(f.file, &iter, flags);
+                kfree(iov);
         }
-        return do_vmsplice(fd, iov, nr_segs, flags);
+        fdput(f);
+        return error;
 }
 #endif