Re: [PATCH v3 1/1] drm/ttm: Fix COW check

Christian König <ckoenig.leichtzumerken@xxxxxxxxx> · Fri, 23 Jul 2021 10:33:48 +0200

Am 23.07.21 um 10:21 schrieb Daniel Vetter:
On Wed, Jul 14, 2021 at 10:51 AM Christian König
<christian.koenig@xxxxxxx> wrote:


Am 13.07.21 um 17:28 schrieb Alex Deucher:
On Tue, Jul 13, 2021 at 2:57 AM Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:

Am 13.07.21 um 00:06 schrieb Felix Kuehling:
KFD Thunk maps invisible VRAM BOs with PROT_NONE, MAP_PRIVATE.
is_cow_mapping returns true for these mappings. Add a check for
vm_flags & VM_WRITE to avoid mmap failures on private read-only or
PROT_NONE mappings.

v2: protect against mprotect making a mapping writable after the fact
v3: update driver-specific vm_operations_structs

Fixes: f91142c62161 ("drm/ttm: nuke VM_MIXEDMAP on BO mappings v3")
Signed-off-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
Are you planning to push this to drm-misc?
Yes, just didn't found time yesterday.
This is pushed to the wrong tree drm-misc-next-fixes, should have been
in drm-misc-fixes. Please be careful with that because every time that
goes wrong the script gets confused about which the current tree is,
and pushes the wrong tree to linux-next branches.

I'm going to hard-reset drm-misc-next-fixes now and hope that's good
enough to fix things up (since Thomas is not around all the time for
this merge window).

STOP! I'm about to push a revert for this patch.

And yes that was pushed to the wrong branch, but it turned out that this 
was fortunate since the patch doesn't work correctly.

Christian.

-Daniel


Christian.

Alex

---
    drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c  |  3 ++-
    drivers/gpu/drm/nouveau/nouveau_gem.c    |  3 ++-
    drivers/gpu/drm/radeon/radeon_gem.c      |  3 ++-
    drivers/gpu/drm/ttm/ttm_bo_vm.c          | 14 +++++++++++++-
    drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c |  1 +
    include/drm/ttm/ttm_bo_api.h             |  4 ++++
    6 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index b3404c43a911..1aa750a6a5d2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -79,7 +79,8 @@ static const struct vm_operations_struct amdgpu_gem_vm_ops = {
        .fault = amdgpu_gem_fault,
        .open = ttm_bo_vm_open,
        .close = ttm_bo_vm_close,
-     .access = ttm_bo_vm_access
+     .access = ttm_bo_vm_access,
+     .mprotect = ttm_bo_vm_mprotect
    };

    static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 5b27845075a1..164ea564bb7a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -70,7 +70,8 @@ static const struct vm_operations_struct nouveau_ttm_vm_ops = {
        .fault = nouveau_ttm_fault,
        .open = ttm_bo_vm_open,
        .close = ttm_bo_vm_close,
-     .access = ttm_bo_vm_access
+     .access = ttm_bo_vm_access,
+     .mprotect = ttm_bo_vm_mprotect
    };

    void
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index 458f92a70887..c19ad07eb7b5 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -77,7 +77,8 @@ static const struct vm_operations_struct radeon_gem_vm_ops = {
        .fault = radeon_gem_fault,
        .open = ttm_bo_vm_open,
        .close = ttm_bo_vm_close,
-     .access = ttm_bo_vm_access
+     .access = ttm_bo_vm_access,
+     .mprotect = ttm_bo_vm_mprotect
    };

    static void radeon_gem_object_free(struct drm_gem_object *gobj)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index f56be5bc0861..fb325bad5db6 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -542,17 +542,29 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
    }
    EXPORT_SYMBOL(ttm_bo_vm_access);

+int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
+                    unsigned long end, unsigned long newflags)
+{
+     /* Enforce no COW since would have really strange behavior with it. */
+     if (is_cow_mapping(newflags) && (newflags & VM_WRITE))
+             return -EINVAL;
+
+     return 0;
+}
+EXPORT_SYMBOL(ttm_bo_vm_mprotect);
+
    static const struct vm_operations_struct ttm_bo_vm_ops = {
        .fault = ttm_bo_vm_fault,
        .open = ttm_bo_vm_open,
        .close = ttm_bo_vm_close,
        .access = ttm_bo_vm_access,
+     .mprotect = ttm_bo_vm_mprotect,
    };

    int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
    {
        /* Enforce no COW since would have really strange behavior with it. */
-     if (is_cow_mapping(vma->vm_flags))
+     if (is_cow_mapping(vma->vm_flags) && (vma->vm_flags & VM_WRITE))
                return -EINVAL;

        ttm_bo_get(bo);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
index e6b1f98ec99f..e4bf7dc99320 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
@@ -61,6 +61,7 @@ int vmw_mmap(struct file *filp, struct vm_area_struct *vma)
                .fault = vmw_bo_vm_fault,
                .open = ttm_bo_vm_open,
                .close = ttm_bo_vm_close,
+             .mprotect = ttm_bo_vm_mprotect,
    #ifdef CONFIG_TRANSPARENT_HUGEPAGE
                .huge_fault = vmw_bo_vm_huge_fault,
    #endif
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index f681bbdbc698..40eb95875355 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -605,6 +605,10 @@ void ttm_bo_vm_close(struct vm_area_struct *vma);

    int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
                     void *buf, int len, int write);
+
+int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
+                    unsigned long end, unsigned long newflags);
+
    bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all);

    vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);


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