fix a kmap leak in virtio_console

While we are at it, don't do kmap() under kmap_atomic(), *especially*
for a page we'd allocated with GFP_KERNEL.  It's spelled "page_address",
and had that been more than that, we'd have a real trouble - kmap_high()
can block, and doing that while holding kmap_atomic() is a Bad Idea(tm).

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

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index feea87c..6928d09 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -890,12 +890,10 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
        } else {
                /* Failback to copying a page */
                struct page *page = alloc_page(GFP_KERNEL);
-               char *src = buf->ops->map(pipe, buf, 1);
-               char *dst;
+               char *src;
 
                if (!page)
                        return -ENOMEM;
-               dst = kmap(page);
 
                offset = sd->pos & ~PAGE_MASK;
 
@@ -903,9 +901,8 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
                if (len + offset > PAGE_SIZE)
                        len = PAGE_SIZE - offset;
 
-               memcpy(dst + offset, src + buf->offset, len);
-
-               kunmap(page);
+               src = buf->ops->map(pipe, buf, 1);
+               memcpy(page_address(page) + offset, src + buf->offset, len);
                buf->ops->unmap(pipe, buf, src);
 
                sg_set_page(&(sgl->sg[sgl->n]), page, len, offset);