* @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.
*
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);
*/
mark_page_accessed(page);
out:
- page_cache_release(page);
unlock_page(page);
+out_release:
+ page_cache_release(page);
out_ret:
return ret;
}
* 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.
*
*/
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(¤t->mm->mmap_sem);
+ partial = copy_from_user(dst, src, n);
+ down_read(¤t->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
{
int buffers = 0, error = 0;
- /*
- * It's ok to take the mmap_sem for reading, even
- * across a "get_user()".
- */
down_read(¤t->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;