From: Christian König <christian.koenig@amd.com>
Date: Fri, 9 Oct 2020 13:08:55 +0000 (+0200)
Subject: mm: mmap: fix fput in error path v2
X-Git-Tag: microblaze-v5.12~29^2~7^2~49
X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=1527f926fd04;p=linux-2.6-microblaze.git

mm: mmap: fix fput in error path v2

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/
---

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 0eb80c1ecdab..282bd8b84170 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 d91ecb00d38c..30a4e8412a58 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);