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drm/exynos: fix wrong pointer access at vm close.

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This patch fixes wrong pointer access issue to filp->f_op and
filp->private_data.

The exynos_drm_gem_mmap_ioctl() changes filp->f_op and
filp->private_data temporarily and restore them to use
original ones in exynos_drm_gem_mmap_buffer() but there
was no lock between the changing and the restoring so
wrong pointer access to filp->f_op and filp->private_data
was induced by vm close callback.

So this patch uses mutex lock properly to resolve this issue.

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
This commit is contained in:
YoungJun Cho 2013-02-07 16:17:54 +09:00 committed by Inki Dae
parent e44a5c0016
commit 5af9f116e6
1 changed files with 21 additions and 12 deletions
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33
drivers/gpu/drm/exynos/exynos_drm_gem.c
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@ -329,17 +329,11 @@ static struct drm_file *exynos_drm_find_drm_file(struct drm_device *drm_dev,
{
struct drm_file *file_priv;
mutex_lock(&drm_dev->struct_mutex);
/* find current process's drm_file from filelist. */
list_for_each_entry(file_priv, &drm_dev->filelist, lhead) {
if (file_priv->filp == filp) {
mutex_unlock(&drm_dev->struct_mutex);
list_for_each_entry(file_priv, &drm_dev->filelist, lhead)
if (file_priv->filp == filp)
return file_priv;
}
}
mutex_unlock(&drm_dev->struct_mutex);
WARN_ON(1);
return ERR_PTR(-EFAULT);
@ -400,9 +394,7 @@ static int exynos_drm_gem_mmap_buffer(struct file *filp,
*/
drm_gem_object_reference(obj);
mutex_lock(&drm_dev->struct_mutex);
drm_vm_open_locked(drm_dev, vma);
mutex_unlock(&drm_dev->struct_mutex);
return 0;
}
@ -431,6 +423,16 @@ int exynos_drm_gem_mmap_ioctl(struct drm_device *dev, void *data,
return -EINVAL;
}
/*
* We have to use gem object and its fops for specific mmaper,
* but vm_mmap() can deliver only filp. So we have to change
* filp->f_op and filp->private_data temporarily, then restore
* again. So it is important to keep lock until restoration the
* settings to prevent others from misuse of filp->f_op or
* filp->private_data.
*/
mutex_lock(&dev->struct_mutex);
/*
* Set specific mmper's fops. And it will be restored by
* exynos_drm_gem_mmap_buffer to dev->driver->fops.
@ -448,13 +450,20 @@ int exynos_drm_gem_mmap_ioctl(struct drm_device *dev, void *data,
addr = vm_mmap(file_priv->filp, 0, args->size,
PROT_READ | PROT_WRITE, MAP_SHARED, 0);
drm_gem_object_unreference_unlocked(obj);
drm_gem_object_unreference(obj);
if (IS_ERR((void *)addr)) {
file_priv->filp->private_data = file_priv;
/* check filp->f_op, filp->private_data are restored */
if (file_priv->filp->f_op == &exynos_drm_gem_fops) {
file_priv->filp->f_op = fops_get(dev->driver->fops);
file_priv->filp->private_data = file_priv;
}
mutex_unlock(&dev->struct_mutex);
return PTR_ERR((void *)addr);
}
mutex_unlock(&dev->struct_mutex);
args->mapped = addr;
DRM_DEBUG_KMS("mapped = 0x%lx\n", (unsigned long)args->mapped);