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 [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Christophe JAILLET <[email protected]>
---
Compile tested only.
Also, I don't think that 'cb' is a great name and the associated kernel-doc
description could certainly be improved.
Any proposal welcomed :)
---
drivers/dma-buf/dma-fence-array.c | 10 ++++------
include/linux/dma-fence-array.h | 3 +++
2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index 9b3ce8948351..9c55afaca607 100644
--- 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->cb;
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, cb, 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 ec7f25def392..a793f9d5c73b 100644
--- 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
+ * @cb: 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 cb[] __counted_by(num_fences);
};
/**
--
2.45.1
On Sat, May 18, 2024 at 07:47:02PM +0200, Christophe JAILLET wrote:
> 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 [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Christophe JAILLET <[email protected]>
Yes please! :)
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
Am 18.05.24 um 19:47 schrieb Christophe JAILLET:
> 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 [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Christophe JAILLET <[email protected]>
> ---
> Compile tested only.
>
> Also, I don't think that 'cb' is a great name and the associated kernel-doc
> description could certainly be improved.
> Any proposal welcomed :)
Ah, yes. That was also on my TODO list for a very long time.
> ---
> drivers/dma-buf/dma-fence-array.c | 10 ++++------
> include/linux/dma-fence-array.h | 3 +++
> 2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
> index 9b3ce8948351..9c55afaca607 100644
> --- 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->cb;
> 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, cb, 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 ec7f25def392..a793f9d5c73b 100644
> --- 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
> + * @cb: 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 cb[] __counted_by(num_fences);
Please name that callbacks, apart from that looks good to me.
Regards,
Christian.
> };
>
> /**