vfs: fix vmplice_to_user()

Commit 6130f5315ee8 "switch vmsplice_to_user() to copy_page_to_iter()" in
v3.15-rc1 broke vmsplice(2).

This patch fixes two bugs:

 - count is not initialized to a proper value, which resulted in no data
   being copied

 - if rw_copy_check_uvector() returns negative then the iov might be leaked.

Tested OK.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 9bc07d2b53cf..e246954ea48c 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1537,7 +1537,7 @@ static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
         struct iovec iovstack[UIO_FASTIOV];
         struct iovec *iov = iovstack;
         struct iov_iter iter;
-        ssize_t count = 0;
+        ssize_t count;
 
         pipe = get_pipe_info(file);
         if (!pipe)
@@ -1546,8 +1546,9 @@ static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
         ret = rw_copy_check_uvector(READ, uiov, nr_segs,
                                     ARRAY_SIZE(iovstack), iovstack, &iov);
         if (ret <= 0)
-                return ret;
+                goto out;
 
+        count = ret;
         iov_iter_init(&iter, iov, nr_segs, count, 0);
 
         sd.len = 0;
@@ -1560,6 +1561,7 @@ static long vmsplice_to_user(struct file *file, const struct iovec __user *uiov,
         ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
         pipe_unlock(pipe);
 
+out:
         if (iov != iovstack)
                 kfree(iov);