[PATCH v2 3/4] drm/amdgpu: Check if fd really is an amdgpu fd.

[Bas Nieuwenhuizen]

Otherwise we interpret the file private data as drm & amdgpu data
while it might not be, possibly allowing one to get memory corruption.

Signed-off-by: Bas Nieuwenhuizen <b...@basnieuwenhuizen.nl>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h       |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c   | 16 ++++++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c | 10 +++++++---
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index d67f8b1dfe80..17290cdb8ed8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -411,6 +411,8 @@ struct amdgpu_fpriv {
        struct amdgpu_ctx_mgr   ctx_mgr;
 };
 
+int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv);
+
 int amdgpu_ib_get(struct amdgpu_device *adev, struct amdgpu_vm *vm,
                  unsigned size, struct amdgpu_ib *ib);
 void amdgpu_ib_free(struct amdgpu_device *adev, struct amdgpu_ib *ib,
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index c806f984bcc5..90a520034c89 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -1176,6 +1176,22 @@ static const struct file_operations 
amdgpu_driver_kms_fops = {
 #endif
 };
 
+int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv)
+{
+        struct drm_file *file;
+
+       if (!filp)
+               return -EINVAL;
+
+       if (filp->f_op != &amdgpu_driver_kms_fops) {
+               return -EINVAL;
+       }
+
+       file = filp->private_data;
+       *fpriv = file->driver_priv;
+       return 0;
+}
+
 static bool
 amdgpu_get_crtc_scanout_position(struct drm_device *dev, unsigned int pipe,
                                 bool in_vblank_irq, int *vpos, int *hpos,
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c
index 1cafe8d83a4d..0b70410488b6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c
@@ -54,16 +54,20 @@ static int amdgpu_sched_process_priority_override(struct 
amdgpu_device *adev,
                                                  enum drm_sched_priority 
priority)
 {
        struct file *filp = fget(fd);
-       struct drm_file *file;
        struct amdgpu_fpriv *fpriv;
        struct amdgpu_ctx *ctx;
        uint32_t id;
+       int r;
 
        if (!filp)
                return -EINVAL;
 
-       file = filp->private_data;
-       fpriv = file->driver_priv;
+       r = amdgpu_file_to_fpriv(filp, &fpriv);
+       if (r) {
+               fput(filp);
+               return r;
+       }
+
        idr_for_each_entry(&fpriv->ctx_mgr.ctx_handles, ctx, id)
                amdgpu_ctx_priority_override(ctx, priority);
 
-- 
2.20.1

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