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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>
Link: https://patchwork.freedesktop.org/patch/394772/
This commit is contained in:
Christian König 2020-10-09 15:08:55 +02:00
parent ea86f3defd
commit 0227da01f2
2 changed files with 4 additions and 18 deletions
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20
drivers/dma-buf/dma-buf.c
View File

@ -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);

2
mm/mmap.c
View File

@ -1899,8 +1899,8 @@ 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);