linux-kernel - Re: [PATCH 1/2] Revert "udmabuf: fix vmap

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Message-ID: <c752a31d-e7c5-49bf-8722-8eeaf582a4d1@vivo.com>
Date: Wed, 23 Apr 2025 15:26:37 +0800
From: Huan Yang <link@...o.com>
To: "Kasireddy, Vivek" <vivek.kasireddy@...el.com>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 Gerd Hoffmann <kraxel@...hat.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Dave Airlie <airlied@...hat.com>,
 "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: "opensource.kernel@...o.com" <opensource.kernel@...o.com>,
 Bingbu Cao <bingbu.cao@...ux.intel.com>
Subject: Re: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set"

 From 38aa11d92f209e7529736f3e11e08dfc804bdfae Mon Sep 17 00:00:00 2001
From: Huan Yang <link@...o.com>
Date: Tue, 15 Apr 2025 10:04:18 +0800
Subject: [PATCH 1/2] Revert "udmabuf: fix vmap_udmabuf error page set"

This reverts commit 18d7de823b7150344d242c3677e65d68c5271b04.

This given a misuse of vmap_pfn, vmap_pfn give a !pfn_valid check
to avoid user miss use it. This API design to only for none-page struct
based user invoke, i.e. PCIe BARs and other. So any page based will
inject by !pfn_valid check.

udmabuf used shmem or hugetlb as folio src, hence, page/folio based,
can't use it.

Signed-off-by: Huan Yang <link@...o.com>
Reported-by: Bingbu Cao <bingbu.cao@...ux.intel.com>
Closes: https://lore.kernel.org/dri-devel/eb7e0137-3508-4287-98c4-816c5fd98e10@vivo.com/T/#mbda4f64a3532b32e061f4e8763bc8e307bea3ca8
Acked-by: Vivek Kasireddy <vivek.kasireddy@...el.com>
---
  drivers/dma-buf/Kconfig   |  1 -
  drivers/dma-buf/udmabuf.c | 22 +++++++---------------
  2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
index fee04fdb0822..b46eb8a552d7 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -36,7 +36,6 @@ config UDMABUF
      depends on DMA_SHARED_BUFFER
      depends on MEMFD_CREATE || COMPILE_TEST
      depends on MMU
-    select VMAP_PFN
      help
        A driver to let userspace turn memfd regions into dma-bufs.
        Qemu can use this to create host dmabufs for guest framebuffers.
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 7eee3eb47a8e..79845565089d 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -109,29 +109,21 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
  static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
  {
      struct udmabuf *ubuf = buf->priv;
-    unsigned long *pfns;
+    struct page **pages;
      void *vaddr;
      pgoff_t pg;

      dma_resv_assert_held(buf->resv);

-    /**
-     * HVO may free tail pages, so just use pfn to map each folio
-     * into vmalloc area.
-     */
-    pfns = kvmalloc_array(ubuf->pagecount, sizeof(*pfns), GFP_KERNEL);
-    if (!pfns)
+    pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);
+    if (!pages)
          return -ENOMEM;

-    for (pg = 0; pg < ubuf->pagecount; pg++) {
-        unsigned long pfn = folio_pfn(ubuf->folios[pg]);
-
-        pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
-        pfns[pg] = pfn;
-    }
+    for (pg = 0; pg < ubuf->pagecount; pg++)
+        pages[pg] = &ubuf->folios[pg]->page;

-    vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
-    kvfree(pfns);
+    vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
+    kvfree(pages);
      if (!vaddr)
          return -EINVAL;

--
2.48.1