dma-buf/fence-array: Add flex array to struct dma_fence_array

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].

The "struct dma_fence_array" can be refactored to add a flex array in order
to have the "callback structures allocated behind the array" be more
explicit.

Do so:
   - makes the code more readable and safer.
   - allows using __counted_by() for additional checks
   - avoids some pointer arithmetic in dma_fence_array_enable_signaling()

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/8b4e556e07b5dd78bb8a39b67ea0a43b199083c8.1716652811.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christian König <christian.koenig@amd.com>

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index 9b3ce8948351cb581df89e9834820ad2bb536a79..c74ac197d5fea1dd3a83e3350e3dac05bd9f00a2 100644 (file)
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -70,7 +70,7 @@ static void dma_fence_array_cb_func(struct dma_fence *f,
 static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
 {
        struct dma_fence_array *array = to_dma_fence_array(fence);
-       struct dma_fence_array_cb *cb = (void *)(&array[1]);
+       struct dma_fence_array_cb *cb = array->callbacks;
        unsigned i;
 
        for (i = 0; i < array->num_fences; ++i) {
@@ -168,22 +168,20 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
                                               bool signal_on_any)
 {
        struct dma_fence_array *array;
-       size_t size = sizeof(*array);
 
        WARN_ON(!num_fences || !fences);
 
-       /* Allocate the callback structures behind the array. */
-       size += num_fences * sizeof(struct dma_fence_array_cb);
-       array = kzalloc(size, GFP_KERNEL);
+       array = kzalloc(struct_size(array, callbacks, num_fences), GFP_KERNEL);
        if (!array)
                return NULL;
 
+       array->num_fences = num_fences;
+
        spin_lock_init(&array->lock);
        dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock,
                       context, seqno);
        init_irq_work(&array->work, irq_dma_fence_array_work);
 
-       array->num_fences = num_fences;
        atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences);
        array->fences = fences;
 

diff --git a/include/linux/dma-fence-array.h b/include/linux/dma-fence-array.h
index ec7f25def39290cfb331f0350f431cd8afd249b6..29c5650c10384bb9bb6ed573e5c84ab6c46443d1 100644 (file)
--- a/include/linux/dma-fence-array.h
+++ b/include/linux/dma-fence-array.h
@@ -33,6 +33,7 @@ struct dma_fence_array_cb {
  * @num_pending: fences in the array still pending
  * @fences: array of the fences
  * @work: internal irq_work function
+ * @callbacks: array of callback helpers
  */
 struct dma_fence_array {
        struct dma_fence base;
@@ -43,6 +44,8 @@ struct dma_fence_array {
        struct dma_fence **fences;
 
        struct irq_work work;
+
+       struct dma_fence_array_cb callbacks[] __counted_by(num_fences);
 };
 
 /**