[PATCH 1/6] mm: mmap: fix fput in error path

[Christian König]

Patch "495c10cc1c0c CHROMIUM: dma-buf: restore args..."
adds a workaround for a bug in mmap_region.

As the comment states ->mmap() callback can change
vma->vm_file and so we might call fput() on the wrong file.

Revert the workaround and proper fix this in mmap_region.

Signed-off-by: Christian König <christian.koe...@amd.com>
---
 drivers/dma-buf/dma-buf.c | 22 +++++-----------------
 mm/mmap.c                 |  2 +-
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index a6ba4d598f0e..edd57402a48a 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1143,9 +1143,6 @@ EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
                 unsigned long pgoff)
 {
-       struct file *oldfile;
-       int ret;
-
        if (WARN_ON(!dmabuf || !vma))
                return -EINVAL;
 
@@ -1163,22 +1160,13 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct 
vm_area_struct *vma,
                return -EINVAL;
 
        /* readjust the vma */
-       get_file(dmabuf->file);
-       oldfile = vma->vm_file;
-       vma->vm_file = dmabuf->file;
-       vma->vm_pgoff = pgoff;
+       if (vma->vm_file)
+               fput(vma->vm_file);
 
-       ret = dmabuf->ops->mmap(dmabuf, vma);
-       if (ret) {
-               /* restore old parameters on failure */
-               vma->vm_file = oldfile;
-               fput(dmabuf->file);
-       } else {
-               if (oldfile)
-                       fput(oldfile);
-       }
-       return ret;
+       vma->vm_file = get_file(dmabuf->file);
+       vma->vm_pgoff = pgoff;
 
+       return dmabuf->ops->mmap(dmabuf, vma);
 }
 EXPORT_SYMBOL_GPL(dma_buf_mmap);
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 40248d84ad5f..3a2670d73355 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1852,8 +1852,8 @@ unsigned long mmap_region(struct file *file, unsigned 
long addr,
        return addr;
 
 unmap_and_free_vma:
+       fput(vma->vm_file);
        vma->vm_file = NULL;
-       fput(file);
 
        /* Undo any partial mapping done by a device driver. */
        unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
-- 
2.17.1

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