Re: [PATCH] xen/gntdev: Fix the abuse of underlying struct page in DMA-buf import
From: kernel test robot
Date: Sat Jan 06 2024 - 08:57:17 EST
Hi Oleksandr,
kernel test robot noticed the following build warnings:
[auto build test WARNING on xen-tip/linux-next]
[also build test WARNING on linus/master v6.7-rc8 next-20240105]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Oleksandr-Tyshchenko/xen-gntdev-Fix-the-abuse-of-underlying-struct-page-in-DMA-buf-import/20240105-025516
base: https://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git linux-next
patch link: https://lore.kernel.org/r/20240104185327.177376-1-olekstysh%40gmail.com
patch subject: [PATCH] xen/gntdev: Fix the abuse of underlying struct page in DMA-buf import
config: x86_64-allmodconfig (https://download.01.org/0day-ci/archive/20240106/202401062122.it6zvLG0-lkp@xxxxxxxxx/config)
compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240106/202401062122.it6zvLG0-lkp@xxxxxxxxx/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401062122.it6zvLG0-lkp@xxxxxxxxx/
All warnings (new ones prefixed by >>):
>> drivers/xen/gntdev-dmabuf.c:623:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
623 | if (!gfns)
| ^~~~~
drivers/xen/gntdev-dmabuf.c:660:9: note: uninitialized use occurs here
660 | return ret;
| ^~~
drivers/xen/gntdev-dmabuf.c:623:2: note: remove the 'if' if its condition is always false
623 | if (!gfns)
| ^~~~~~~~~~
624 | goto fail_unmap;
| ~~~~~~~~~~~~~~~
drivers/xen/gntdev-dmabuf.c:569:43: note: initialize the variable 'ret' to silence this warning
569 | struct gntdev_dmabuf *gntdev_dmabuf, *ret;
| ^
| = NULL
1 warning generated.
vim +623 drivers/xen/gntdev-dmabuf.c
564
565 static struct gntdev_dmabuf *
566 dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev,
567 int fd, int count, int domid)
568 {
569 struct gntdev_dmabuf *gntdev_dmabuf, *ret;
570 struct dma_buf *dma_buf;
571 struct dma_buf_attachment *attach;
572 struct sg_table *sgt;
573 struct sg_dma_page_iter sg_iter;
574 unsigned long *gfns;
575 int i;
576
577 dma_buf = dma_buf_get(fd);
578 if (IS_ERR(dma_buf))
579 return ERR_CAST(dma_buf);
580
581 gntdev_dmabuf = dmabuf_imp_alloc_storage(count);
582 if (IS_ERR(gntdev_dmabuf)) {
583 ret = gntdev_dmabuf;
584 goto fail_put;
585 }
586
587 gntdev_dmabuf->priv = priv;
588 gntdev_dmabuf->fd = fd;
589
590 attach = dma_buf_attach(dma_buf, dev);
591 if (IS_ERR(attach)) {
592 ret = ERR_CAST(attach);
593 goto fail_free_obj;
594 }
595
596 gntdev_dmabuf->u.imp.attach = attach;
597
598 sgt = dma_buf_map_attachment_unlocked(attach, DMA_BIDIRECTIONAL);
599 if (IS_ERR(sgt)) {
600 ret = ERR_CAST(sgt);
601 goto fail_detach;
602 }
603
604 /* Check that we have zero offset. */
605 if (sgt->sgl->offset) {
606 ret = ERR_PTR(-EINVAL);
607 pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n",
608 sgt->sgl->offset);
609 goto fail_unmap;
610 }
611
612 /* Check number of pages that imported buffer has. */
613 if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) {
614 ret = ERR_PTR(-EINVAL);
615 pr_debug("DMA buffer has %zu pages, user-space expects %d\n",
616 attach->dmabuf->size, gntdev_dmabuf->nr_pages);
617 goto fail_unmap;
618 }
619
620 gntdev_dmabuf->u.imp.sgt = sgt;
621
622 gfns = kcalloc(count, sizeof(*gfns), GFP_KERNEL);
> 623 if (!gfns)
624 goto fail_unmap;
625
626 /* Now convert sgt to array of gfns without accessing underlying pages. */
627 i = 0;
628 for_each_sgtable_dma_page(sgt, &sg_iter, 0) {
629 dma_addr_t addr = sg_page_iter_dma_address(&sg_iter);
630 unsigned long pfn = bfn_to_pfn(XEN_PFN_DOWN(dma_to_phys(dev, addr)));
631
632 gfns[i++] = pfn_to_gfn(pfn);
633 }
634
635 ret = ERR_PTR(dmabuf_imp_grant_foreign_access(gfns,
636 gntdev_dmabuf->u.imp.refs,
637 count, domid));
638 kfree(gfns);
639 if (IS_ERR(ret))
640 goto fail_end_access;
641
642 pr_debug("Imported DMA buffer with fd %d\n", fd);
643
644 mutex_lock(&priv->lock);
645 list_add(&gntdev_dmabuf->next, &priv->imp_list);
646 mutex_unlock(&priv->lock);
647
648 return gntdev_dmabuf;
649
650 fail_end_access:
651 dmabuf_imp_end_foreign_access(gntdev_dmabuf->u.imp.refs, count);
652 fail_unmap:
653 dma_buf_unmap_attachment_unlocked(attach, sgt, DMA_BIDIRECTIONAL);
654 fail_detach:
655 dma_buf_detach(dma_buf, attach);
656 fail_free_obj:
657 dmabuf_imp_free_storage(gntdev_dmabuf);
658 fail_put:
659 dma_buf_put(dma_buf);
660 return ret;
661 }
662
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki