genwqe: Take R/W permissions into account when dealing with memory pages

Currently we assume userspace pages are always writable when doing
memory pinning. This is not true, specially since userspace applications
may allocate their memory the way they want, we have no control over it.
If a read-only page is set for pinning, currently the driver fails due
to get_user_pages_fast() refusing to map read-only pages as writable.

This patch changes this behavior, by taking the permission flags of the
pages into account in both pinning/unpinning process, as well as in the
DMA data copy-back to userpace (which we shouldn't try to do blindly,
since it will fail in case of read-only-pages).

Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 27 insertions, 16 deletions

diff --git a/drivers/misc/genwqe/card_utils.c b/drivers/misc/genwqe/card_utils.c
index 147b83011b58..5c0d917636f7 100644
--- a/drivers/misc/genwqe/card_utils.c
+++ b/drivers/misc/genwqe/card_utils.c
@@ -296,7 +296,7 @@ static int genwqe_sgl_size(int num_pages)
  * from user-space into the cached pages.
  */
 int genwqe_alloc_sync_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl,
-			  void __user *user_addr, size_t user_size)
+			  void __user *user_addr, size_t user_size, int write)
 {
 	int rc;
 	struct pci_dev *pci_dev = cd->pci_dev;
@@ -312,6 +312,7 @@ int genwqe_alloc_sync_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl,
 
 	sgl->user_addr = user_addr;
 	sgl->user_size = user_size;
+	sgl->write = write;
 	sgl->sgl_size = genwqe_sgl_size(sgl->nr_pages);
 
 	if (get_order(sgl->sgl_size) > MAX_ORDER) {
@@ -476,14 +477,20 @@ int genwqe_setup_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl,
 int genwqe_free_sync_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl)
 {
 	int rc = 0;
+	size_t offset;
+	unsigned long res;
 	struct pci_dev *pci_dev = cd->pci_dev;
 
 	if (sgl->fpage) {
-		if (copy_to_user(sgl->user_addr, sgl->fpage + sgl->fpage_offs,
-				 sgl->fpage_size)) {
-			dev_err(&pci_dev->dev, "[%s] err: copying fpage!\n",
-				__func__);
-			rc = -EFAULT;
+		if (sgl->write) {
+			res = copy_to_user(sgl->user_addr,
+				sgl->fpage + sgl->fpage_offs, sgl->fpage_size);
+			if (res) {
+				dev_err(&pci_dev->dev,
+					"[%s] err: copying fpage! (res=%lu)\n",
+					__func__, res);
+				rc = -EFAULT;
+			}
 		}
 		__genwqe_free_consistent(cd, PAGE_SIZE, sgl->fpage,
 					 sgl->fpage_dma_addr);
@@ -491,12 +498,16 @@ int genwqe_free_sync_sgl(struct genwqe_dev *cd, struct genwqe_sgl *sgl)
 		sgl->fpage_dma_addr = 0;
 	}
 	if (sgl->lpage) {
-		if (copy_to_user(sgl->user_addr + sgl->user_size -
-				 sgl->lpage_size, sgl->lpage,
-				 sgl->lpage_size)) {
-			dev_err(&pci_dev->dev, "[%s] err: copying lpage!\n",
-				__func__);
-			rc = -EFAULT;
+		if (sgl->write) {
+			offset = sgl->user_size - sgl->lpage_size;
+			res = copy_to_user(sgl->user_addr + offset, sgl->lpage,
+					   sgl->lpage_size);
+			if (res) {
+				dev_err(&pci_dev->dev,
+					"[%s] err: copying lpage! (res=%lu)\n",
+					__func__, res);
+				rc = -EFAULT;
+			}
 		}
 		__genwqe_free_consistent(cd, PAGE_SIZE, sgl->lpage,
 					 sgl->lpage_dma_addr);
@@ -599,14 +610,14 @@ int genwqe_user_vmap(struct genwqe_dev *cd, struct dma_mapping *m, void *uaddr,
 	/* pin user pages in memory */
 	rc = get_user_pages_fast(data & PAGE_MASK, /* page aligned addr */
 				 m->nr_pages,
-				 1,		/* write by caller */
+				 m->write,		/* readable/writable */
 				 m->page_list);	/* ptrs to pages */
 	if (rc < 0)
 		goto fail_get_user_pages;
 
 	/* assumption: get_user_pages can be killed by signals. */
 	if (rc < m->nr_pages) {
-		free_user_pages(m->page_list, rc, 0);
+		free_user_pages(m->page_list, rc, m->write);
 		rc = -EFAULT;
 		goto fail_get_user_pages;
 	}
@@ -618,7 +629,7 @@ int genwqe_user_vmap(struct genwqe_dev *cd, struct dma_mapping *m, void *uaddr,
 	return 0;
 
  fail_free_user_pages:
-	free_user_pages(m->page_list, m->nr_pages, 0);
+	free_user_pages(m->page_list, m->nr_pages, m->write);
 
  fail_get_user_pages:
 	kfree(m->page_list);
@@ -651,7 +662,7 @@ int genwqe_user_vunmap(struct genwqe_dev *cd, struct dma_mapping *m,
 		genwqe_unmap_pages(cd, m->dma_list, m->nr_pages);
 
 	if (m->page_list) {
-		free_user_pages(m->page_list, m->nr_pages, 1);
+		free_user_pages(m->page_list, m->nr_pages, m->write);
 
 		kfree(m->page_list);
 		m->page_list = NULL;