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xen/gntdev: Fix the abuse of underlying struct page in DMA-buf import

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DO NOT access the underlying struct page of an sg table exported
by DMA-buf in dmabuf_imp_to_refs(), this is not allowed.
Please see drivers/dma-buf/dma-buf.c:mangle_sg_table() for details.

Fortunately, here (for special Xen device) we can avoid using
pages and calculate gfns directly from dma addresses provided by
the sg table.

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Link: https://lore.kernel.org/r/20240107103426.2038075-1-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Oleksandr Tyshchenko 2024-01-07 12:34:26 +02:00 committed by Juergen Gross
parent f1479f0a4f
commit 2d2db7d402
1 changed files with 27 additions and 27 deletions
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48
drivers/xen/gntdev-dmabuf.c
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@ -11,6 +11,7 @@
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/dma-buf.h>
#include <linux/dma-direct.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
@ -50,7 +51,7 @@ struct gntdev_dmabuf {
/* Number of pages this buffer has. */
int nr_pages;
/* Pages of this buffer. */
/* Pages of this buffer (only for dma-buf export). */
struct page **pages;
};
@ -484,7 +485,7 @@ out:
/* DMA buffer import support. */
static int
dmabuf_imp_grant_foreign_access(struct page **pages, u32 *refs,
dmabuf_imp_grant_foreign_access(unsigned long *gfns, u32 *refs,
int count, int domid)
{
grant_ref_t priv_gref_head;
@ -507,7 +508,7 @@ dmabuf_imp_grant_foreign_access(struct page **pages, u32 *refs,
}
gnttab_grant_foreign_access_ref(cur_ref, domid,
xen_page_to_gfn(pages[i]), 0);
gfns[i], 0);
refs[i] = cur_ref;
}
@ -529,7 +530,6 @@ static void dmabuf_imp_end_foreign_access(u32 *refs, int count)
static void dmabuf_imp_free_storage(struct gntdev_dmabuf *gntdev_dmabuf)
{
kfree(gntdev_dmabuf->pages);
kfree(gntdev_dmabuf->u.imp.refs);
kfree(gntdev_dmabuf);
}
@ -549,12 +549,6 @@ static struct gntdev_dmabuf *dmabuf_imp_alloc_storage(int count)
if (!gntdev_dmabuf->u.imp.refs)
goto fail;
gntdev_dmabuf->pages = kcalloc(count,
sizeof(gntdev_dmabuf->pages[0]),
GFP_KERNEL);
if (!gntdev_dmabuf->pages)
goto fail;
gntdev_dmabuf->nr_pages = count;
for (i = 0; i < count; i++)
@ -576,7 +570,8 @@ dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
struct dma_buf *dma_buf;
struct dma_buf_attachment *attach;
struct sg_table *sgt;
struct sg_page_iter sg_iter;
struct sg_dma_page_iter sg_iter;
unsigned long *gfns;
int i;
dma_buf = dma_buf_get(fd);
@ -624,26 +619,31 @@ dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
gntdev_dmabuf->u.imp.sgt = sgt;
/* Now convert sgt to array of pages and check for page validity. */
i = 0;
for_each_sgtable_page(sgt, &sg_iter, 0) {
struct page *page = sg_page_iter_page(&sg_iter);
/*
* Check if page is valid: this can happen if we are given
* a page from VRAM or other resources which are not backed
* by a struct page.
*/
if (!pfn_valid(page_to_pfn(page))) {
ret = ERR_PTR(-EINVAL);
gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
if (!gfns) {
ret = ERR_PTR(-ENOMEM);
goto fail_unmap;
}
gntdev_dmabuf->pages[i++] = page;
/*
* Now convert sgt to array of gfns without accessing underlying pages.
* It is not allowed to access the underlying struct page of an sg table
* exported by DMA-buf, but since we deal with special Xen dma device here
* (not a normal physical one) look at the dma addresses in the sg table
* and then calculate gfns directly from them.
*/
i = 0;
for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
gfns[i++] = pfn_to_gfn(pfn);
}
ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gntdev_dmabuf->pages,
ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
gntdev_dmabuf->u.imp.refs,
count, domid));
kfree(gfns);
if (IS_ERR(ret))
goto fail_end_access;