From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> [ Upstream commit 2d2db7d40254d5fb53b11ebd703cd1ed0c5de7a1 ] 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@xxxxxxxx> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> Acked-by: Christian König <christian.koenig@xxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> Acked-by: Daniel Vetter <daniel@xxxxxxxx> Link: https://lore.kernel.org/r/20240107103426.2038075-1-olekstysh@xxxxxxxxx Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/xen/gntdev-dmabuf.c | 50 ++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 25 deletions(-) diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c index 940e5e9e8a54..335451309566 100644 --- a/drivers/xen/gntdev-dmabuf.c +++ b/drivers/xen/gntdev-dmabuf.c @@ -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 @@ static int dmabuf_exp_from_refs(struct gntdev_priv *priv, int flags, /* 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. */ + gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL); + if (!gfns) { + ret = ERR_PTR(-ENOMEM); + goto fail_unmap; + } + + /* + * 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_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); - goto fail_unmap; - } + 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))); - gntdev_dmabuf->pages[i++] = page; + 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; -- 2.43.0
