[PATCH 2/2] mm: introduce vma_set_file function v5

From: Christian König
Date: Fri Nov 06 2020 - 06:48:19 EST

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Previous message: Christian König: "[PATCH 1/2] mm: mmap: fix fput in error path v2"
In reply to: Andrew Morton: "Re: [PATCH 1/2] mm: mmap: fix fput in error path v2"
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Add the new vma_set_file() function to allow changing
vma->vm_file with the necessary refcount dance.

v2: add more users of this.
v3: add missing EXPORT_SYMBOL, rebase on mmap cleanup,
add comments why we drop the reference on two occasions.
v4: make it clear that changing an anonymous vma is illegal.
v5: move vma_set_file to mm/util.c

Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> (v2)
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
drivers/dma-buf/dma-buf.c | 3 +--
drivers/gpu/drm/etnaviv/etnaviv_gem.c | 4 +---
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 3 +--
drivers/gpu/drm/i915/gem/i915_gem_mman.c | 5 +++--
drivers/gpu/drm/msm/msm_gem.c | 4 +---
drivers/gpu/drm/omapdrm/omap_gem.c | 3 +--
drivers/gpu/drm/vgem/vgem_drv.c | 3 +--
drivers/staging/android/ashmem.c | 6 +++---
include/linux/mm.h | 2 ++
mm/util.c | 12 ++++++++++++
10 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 282bd8b84170..e63684d4cd90 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1183,8 +1183,7 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
return -EINVAL;

/* readjust the vma */
- fput(vma->vm_file);
- vma->vm_file = get_file(dmabuf->file);
+ vma_set_file(vma, dmabuf->file);
vma->vm_pgoff = pgoff;

return dmabuf->ops->mmap(dmabuf, vma);
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index 67d9a2b9ea6a..4132acfa11be 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -145,10 +145,8 @@ static int etnaviv_gem_mmap_obj(struct etnaviv_gem_object *etnaviv_obj,
* address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs)
*/
- fput(vma->vm_file);
- get_file(etnaviv_obj->base.filp);
vma->vm_pgoff = 0;
- vma->vm_file = etnaviv_obj->base.filp;
+ vma_set_file(vma, etnaviv_obj->base.filp);

vma->vm_page_prot = vm_page_prot;
}
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index 0dd477e56573..04e9c04545ad 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -114,8 +114,7 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
if (ret)
return ret;

- fput(vma->vm_file);
- vma->vm_file = get_file(obj->base.filp);
+ vma_set_file(vma, obj->base.filp);

return 0;
}
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index 3d69e51f3e4d..ec28a6cde49b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -893,8 +893,9 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
* requires avoiding extraneous references to their filp, hence why
* we prefer to use an anonymous file for their mmaps.
*/
- fput(vma->vm_file);
- vma->vm_file = anon;
+ vma_set_file(vma, anon);
+ /* Drop the initial creation reference, the vma is now holding one. */
+ fput(anon);

switch (mmo->mmap_type) {
case I915_MMAP_TYPE_WC:
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 2e1bce7c0b19..311721ceee50 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -212,10 +212,8 @@ int msm_gem_mmap_obj(struct drm_gem_object *obj,
* address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs)
*/
- fput(vma->vm_file);
- get_file(obj->filp);
vma->vm_pgoff = 0;
- vma->vm_file = obj->filp;
+ vma_set_file(vma, obj->filp);

vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
}
diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index d8e09792793a..f063f5a04fb0 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -564,9 +564,8 @@ int omap_gem_mmap_obj(struct drm_gem_object *obj,
* address_space (so unmap_mapping_range does what we want,
* in particular in the case of mmap'd dmabufs)
*/
- fput(vma->vm_file);
vma->vm_pgoff = 0;
- vma->vm_file = get_file(obj->filp);
+ vma_set_file(vma, obj->filp);

vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
}
diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index fa54a6d1403d..ea0eecae5153 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -397,8 +397,7 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
if (ret)
return ret;

- fput(vma->vm_file);
- vma->vm_file = get_file(obj->filp);
+ vma_set_file(vma, obj->filp);
vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
index 10b4be1f3e78..4789d36ddfd3 100644
--- a/drivers/staging/android/ashmem.c
+++ b/drivers/staging/android/ashmem.c
@@ -450,9 +450,9 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
vma_set_anonymous(vma);
}

- if (vma->vm_file)
- fput(vma->vm_file);
- vma->vm_file = asma->file;
+ vma_set_file(vma, asma->file);
+ /* XXX: merge this with the get_file() above if possible */
+ fput(asma->file);

out:
mutex_unlock(&ashmem_mutex);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ef360fe70aaf..2b7ac36c42dd 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2719,6 +2719,8 @@ static inline void vma_set_page_prot(struct vm_area_struct *vma)
}
#endif

+void vma_set_file(struct vm_area_struct *vma, struct file *file);
+
#ifdef CONFIG_NUMA_BALANCING
unsigned long change_prot_numa(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
diff --git a/mm/util.c b/mm/util.c
index 4ddb6e186dd5..8c9b7d1e7c49 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -311,6 +311,18 @@ int vma_is_stack_for_current(struct vm_area_struct *vma)
return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}

+/*
+ * Change backing file, only valid to use during initial VMA setup.
+ */
+void vma_set_file(struct vm_area_struct *vma, struct file *file)
+{
+ /* Changing an anonymous vma with this is illegal */
+ get_file(file);
+ swap(vma->vm_file, file);
+ fput(file);
+}
+EXPORT_SYMBOL(vma_set_file);
+
#ifndef STACK_RND_MASK
#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
#endif
--
2.25.1

Next message: Adrian Ratiu: "Re: [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization"
Previous message: Christian König: "[PATCH 1/2] mm: mmap: fix fput in error path v2"
In reply to: Andrew Morton: "Re: [PATCH 1/2] mm: mmap: fix fput in error path v2"
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