From 1527f926fd04490f648c42f42b45218a04754f87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
Date: Fri, 9 Oct 2020 15:08:55 +0200
Subject: [PATCH] mm: mmap: fix fput in error path v2
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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.
v2: drop the extra if in dma_buf_mmap as well
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://patchwork.freedesktop.org/patch/399359/
---
drivers/dma-buf/dma-buf.c | 20 +++-----------------
mm/mmap.c | 2 +-
2 files changed, 4 insertions(+), 18 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 0eb80c1ecdab3..282bd8b841708 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1166,9 +1166,6 @@ 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;
@@ -1186,22 +1183,11 @@ 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;
+ fput(vma->vm_file);
+ vma->vm_file = get_file(dmabuf->file);
vma->vm_pgoff = pgoff;
- 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;
-
+ return dmabuf->ops->mmap(dmabuf, vma);
}
EXPORT_SYMBOL_GPL(dma_buf_mmap);
diff --git a/mm/mmap.c b/mm/mmap.c
index d91ecb00d38cd..30a4e8412a585 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1899,8 +1899,8 @@ out:
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);
--
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