X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=fs%2Fsplice.c;h=e95a36228863affa3d6c19a37ac4766f8e147412;hb=0fd5355470ea40355b8af76d01748ec7b9926d4d;hp=22496d2a73fa1ab5efe6f663cfc1a92a9a316543;hpb=fdb64f93b38a3470fa4db8cd5720b8c731922d1a;p=linux-2.6

diff --git a/fs/splice.c b/fs/splice.c
index 22496d2a73..e95a362288 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -164,7 +164,7 @@ static const struct pipe_buf_operations user_page_pipe_buf_ops = {
  * @spd:	data to fill
  *
  * Description:
- *    @spd contains a map of pages and len/offset tupples, a long with
+ *    @spd contains a map of pages and len/offset tuples, along with
  *    the struct pipe_buf_operations associated with these pages. This
  *    function will link that data to the pipe.
  *
@@ -594,7 +594,7 @@ find_page:
 		ret = add_to_page_cache_lru(page, mapping, index,
 					    GFP_KERNEL);
 		if (unlikely(ret))
-			goto out;
+			goto out_release;
 	}
 
 	ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
@@ -650,8 +650,9 @@ find_page:
 	 */
 	mark_page_accessed(page);
 out:
-	page_cache_release(page);
 	unlock_page(page);
+out_release:
+	page_cache_release(page);
 out_ret:
 	return ret;
 }
@@ -999,7 +1000,7 @@ static long do_splice_to(struct file *in, loff_t *ppos,
  * Description:
  *    This is a special case helper to splice directly between two
  *    points, without requiring an explicit pipe. Internally an allocated
- *    pipe is cached in the process, and reused during the life time of
+ *    pipe is cached in the process, and reused during the lifetime of
  *    that process.
  *
  */
@@ -1222,6 +1223,33 @@ static long do_splice(struct file *in, loff_t __user *off_in,
 	return -EINVAL;
 }
 
+/*
+ * Do a copy-from-user while holding the mmap_semaphore for reading, in a
+ * manner safe from deadlocking with simultaneous mmap() (grabbing mmap_sem
+ * for writing) and page faulting on the user memory pointed to by src.
+ * This assumes that we will very rarely hit the partial != 0 path, or this
+ * will not be a win.
+ */
+static int copy_from_user_mmap_sem(void *dst, const void __user *src, size_t n)
+{
+	int partial;
+
+	pagefault_disable();
+	partial = __copy_from_user_inatomic(dst, src, n);
+	pagefault_enable();
+
+	/*
+	 * Didn't copy everything, drop the mmap_sem and do a faulting copy
+	 */
+	if (unlikely(partial)) {
+		up_read(&current->mm->mmap_sem);
+		partial = copy_from_user(dst, src, n);
+		down_read(&current->mm->mmap_sem);
+	}
+
+	return partial;
+}
+
 /*
  * Map an iov into an array of pages and offset/length tupples. With the
  * partial_page structure, we can map several non-contiguous ranges into
@@ -1235,31 +1263,26 @@ static int get_iovec_page_array(const struct iovec __user *iov,
 {
 	int buffers = 0, error = 0;
 
-	/*
-	 * It's ok to take the mmap_sem for reading, even
-	 * across a "get_user()".
-	 */
 	down_read(&current->mm->mmap_sem);
 
 	while (nr_vecs) {
 		unsigned long off, npages;
+		struct iovec entry;
 		void __user *base;
 		size_t len;
 		int i;
 
-		/*
-		 * Get user address base and length for this iovec.
-		 */
-		error = get_user(base, &iov->iov_base);
-		if (unlikely(error))
-			break;
-		error = get_user(len, &iov->iov_len);
-		if (unlikely(error))
+		error = -EFAULT;
+		if (copy_from_user_mmap_sem(&entry, iov, sizeof(entry)))
 			break;
 
+		base = entry.iov_base;
+		len = entry.iov_len;
+
 		/*
 		 * Sanity check this iovec. 0 read succeeds.
 		 */
+		error = 0;
 		if (unlikely(!len))
 			break;
 		error = -EFAULT;