The VMA offset manager uses a device-global address-space, hence, any
user can currently map any offset-node they want. They only need to guess
the right offset. If we wanted per open-file offset spaces, we'd either
need VM_NONLINEAR mappings or multiple "struct address_space" trees. As
both doesn't really scale, we implement access management in the VMA
manager itself.
We use an rb-tree to store open-files for each VMA node. On each mmap
call, GEM, TTM or the drivers must check whether the current user is
allowed to map this file.
We add a separate lock for each node as there is no generic lock available
for the caller to protect the node easily.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
drivers/gpu/drm/drm_vma_manager.c | 148 ++++++++++++++++++++++++++++++++++++++
include/drm/drm_vma_manager.h | 16 +++++
2 files changed, 164 insertions(+)
diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c
index d07247e..781f7da 100644
--- a/drivers/gpu/drm/drm_vma_manager.c
+++ b/drivers/gpu/drm/drm_vma_manager.c
@@ -25,6 +25,7 @@
#include <drm/drmP.h>
#include <drm/drm_mm.h>
#include <drm/drm_vma_manager.h>
+#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/rbtree.h>
@@ -58,6 +59,13 @@
* must always be page-aligned (as usual).
* If you want to get a valid byte-based user-space address for a given offset,
* please see drm_vma_node_offset_addr().
+ *
+ * Additionally to offset management, the vma offset manager also handles access
+ * management. For every open-file context that is allowed to access a given
+ * node, you must call drm_vma_node_allow(). Otherwise, an mmap() call on this
+ * open-file with the offset of the node will fail with -EACCES. To revoke
+ * access again, use drm_vma_node_revoke(). However, the caller is responsible
+ * for destroying already existing mappings, if required.
*/
/**
@@ -258,3 +266,143 @@ void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
write_unlock(&mgr->vm_lock);
}
EXPORT_SYMBOL(drm_vma_offset_remove);
+
+/**
+ * drm_vma_node_allow - Add open-file to list of allowed users
+ * @node: Node to modify
+ * @filp: Open file to add
+ *
+ * Add @filp to the list of allowed open-files for this node. If @filp is
+ * already on this list, the ref-count is incremented.
+ *
+ * The list of allowed-users is preserved across drm_vma_offset_add() and
+ * drm_vma_offset_remove() calls. You may even call it if the node is currently
+ * not added to any offset-manager.
+ *
+ * You must remove all open-files the same number of times as you added them
+ * before destroying the node. Otherwise, you will leak memory.
+ *
+ * This is locked against concurrent access internally.
+ *
+ * RETURNS:
+ * 0 on success, negative error code on internal failure (out-of-mem)
+ */
+int drm_vma_node_allow(struct drm_vma_offset_node *node, struct file *filp)
+{
+ struct rb_node **iter;
+ struct rb_node *parent = NULL;
+ struct drm_vma_offset_file *entry;
+ int ret = 0;
+
+ write_lock(&node->vm_lock);
+
+ iter = &node->vm_files.rb_node;
+
+ while (likely(*iter)) {
+ parent = *iter;
+ entry = rb_entry(*iter, struct drm_vma_offset_file, vm_rb);
+
+ if (filp == entry->vm_filp) {
+ entry->vm_count++;
+ goto unlock;
+ } else if (filp > entry->vm_filp) {
+ iter = &(*iter)->rb_right;
+ } else {
+ iter = &(*iter)->rb_left;
+ }
+ }
+
+ entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+
+ entry->vm_filp = filp;
+ entry->vm_count = 1;
+ rb_link_node(&entry->vm_rb, parent, iter);
+ rb_insert_color(&entry->vm_rb, &node->vm_files);
+
+unlock:
+ write_unlock(&node->vm_lock);
+ return ret;
+}
+EXPORT_SYMBOL(drm_vma_node_allow);
+
+/**
+ * drm_vma_node_revoke - Remove open-file from list of allowed users
+ * @node: Node to modify
+ * @filp: Open file to remove
+ *
+ * Decrement the ref-count of @filp in the list of allowed open-files on @node.
+ * If the ref-count drops to zero, remove @filp from the list. You must call
+ * this once for every drm_vma_node_allow() on @filp.
+ *
+ * This is locked against concurrent access internally.
+ *
+ * If @filp is not on the list, nothing is done.
+ */
+void drm_vma_node_revoke(struct drm_vma_offset_node *node, struct file *filp)
+{
+ struct drm_vma_offset_file *entry;
+ struct rb_node *iter;
+
+ write_lock(&node->vm_lock);
+
+ iter = node->vm_files.rb_node;
+ while (likely(iter)) {
+ entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
+ if (filp == entry->vm_filp) {
+ if (!--entry->vm_count) {
+ rb_erase(&entry->vm_rb, &node->vm_files);
+ kfree(entry);
+ }
+ break;
+ } else if (filp > entry->vm_filp) {
+ iter = iter->rb_right;
+ } else {
+ iter = iter->rb_left;
+ }
+ }
+
+ write_unlock(&node->vm_lock);
+}
+EXPORT_SYMBOL(drm_vma_node_revoke);
+
+/**
+ * drm_vma_node_is_allowed - Check whether an open-file is granted access
+ * @node: Node to check
+ * @filp: Open-file to check for
+ *
+ * Search the list in @node whether @filp is currently on the list of allowed
+ * open-files (see drm_vma_node_allow()).
+ *
+ * This is locked against concurrent access internally.
+ *
+ * RETURNS:
+ * true iff @filp is on the list
+ */
+bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
+ struct file *filp)
+{
+ struct drm_vma_offset_file *entry;
+ struct rb_node *iter;
+
+ read_lock(&node->vm_lock);
+
+ iter = node->vm_files.rb_node;
+ while (likely(iter)) {
+ entry = rb_entry(iter, struct drm_vma_offset_file, vm_rb);
+ if (filp == entry->vm_filp)
+ break;
+ else if (filp > entry->vm_filp)
+ iter = iter->rb_right;
+ else
+ iter = iter->rb_left;
+ }
+
+ read_unlock(&node->vm_lock);
+
+ return iter;
+}
+EXPORT_SYMBOL(drm_vma_node_is_allowed);
diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
index 355a0e5..52bb189 100644
--- a/include/drm/drm_vma_manager.h
+++ b/include/drm/drm_vma_manager.h
@@ -24,16 +24,25 @@
*/
#include <drm/drm_mm.h>
+#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/rbtree.h>
#include <linux/spinlock.h>
#include <linux/types.h>
+struct drm_vma_offset_file {
+ struct rb_node vm_rb;
+ struct file *vm_filp;
+ unsigned long vm_count;
+};
+
struct drm_vma_offset_node {
+ rwlock_t vm_lock;
struct drm_mm_node vm_node;
struct rb_node vm_rb;
unsigned long vm_pages;
+ struct rb_root vm_files;
};
struct drm_vma_offset_manager {
@@ -54,6 +63,11 @@ int drm_vma_offset_add(struct drm_vma_offset_manager *mgr,
void drm_vma_offset_remove(struct drm_vma_offset_manager *mgr,
struct drm_vma_offset_node *node);
+int drm_vma_node_allow(struct drm_vma_offset_node *node, struct file *filp);
+void drm_vma_node_revoke(struct drm_vma_offset_node *node, struct file *filp);
+bool drm_vma_node_is_allowed(struct drm_vma_offset_node *node,
+ struct file *filp);
+
/**
* drm_vma_offset_exact_lookup() - Look up node by exact address
* @mgr: Manager object
@@ -85,6 +99,8 @@ drm_vma_offset_exact_lookup(struct drm_vma_offset_manager *mgr,
static inline void drm_vma_node_reset(struct drm_vma_offset_node *node)
{
memset(node, 0, sizeof(*node));
+ node->vm_files = RB_ROOT;
+ rwlock_init(&node->vm_lock);
}
/**
--
1.8.3.2
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