[PATCH v2 1/2] VMCI: Remove handle_arr_calc_size()

[PATCH v2 1/2] VMCI: Remove handle_arr_calc_size()

[Christophe JAILLET]

Use struct_size() instead of handle_arr_calc_size().
This is much more conventional.

While at it, use size_add() when computing the needed size in
vmci_handle_arr_append_entry(). This prevents from (unlikely) overflow
when computing the new size to reallocate.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
Changes in v2:
   - use size_add() in vmci_handle_arr_append_entry()   [Kees Cook]

v1: https://lore.kernel.org/all/adf0c48a57d911be5509688614d2e00694ff57eb.1702068153.git.christophe.jaillet@wanadoo.fr/
---
 drivers/misc/vmw_vmci/vmci_handle_array.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/vmw_vmci/vmci_handle_array.c b/drivers/misc/vmw_vmci/vmci_handle_array.c
index de7fee7ead1b..681b3500125a 100644
--- a/drivers/misc/vmw_vmci/vmci_handle_array.c
+++ b/drivers/misc/vmw_vmci/vmci_handle_array.c
@@ -8,12 +8,6 @@
 #include <linux/slab.h>
 #include "vmci_handle_array.h"
 
-static size_t handle_arr_calc_size(u32 capacity)
-{
-	return VMCI_HANDLE_ARRAY_HEADER_SIZE +
-	    capacity * sizeof(struct vmci_handle);
-}
-
 struct vmci_handle_arr *vmci_handle_arr_create(u32 capacity, u32 max_capacity)
 {
 	struct vmci_handle_arr *array;
@@ -25,7 +19,7 @@ struct vmci_handle_arr *vmci_handle_arr_create(u32 capacity, u32 max_capacity)
 		capacity = min((u32)VMCI_HANDLE_ARRAY_DEFAULT_CAPACITY,
 			       max_capacity);
 
-	array = kmalloc(handle_arr_calc_size(capacity), GFP_ATOMIC);
+	array = kmalloc(struct_size(array, entries, capacity), GFP_ATOMIC);
 	if (!array)
 		return NULL;
 
@@ -51,8 +45,8 @@ int vmci_handle_arr_append_entry(struct vmci_handle_arr **array_ptr,
 		struct vmci_handle_arr *new_array;
 		u32 capacity_bump = min(array->max_capacity - array->capacity,
 					array->capacity);
-		size_t new_size = handle_arr_calc_size(array->capacity +
-						       capacity_bump);
+		size_t new_size = struct_size(array, entries,
+					      size_add(array->capacity, capacity_bump));
 
 		if (array->size >= array->max_capacity)
 			return VMCI_ERROR_NO_MEM;
-- 
2.34.1

[PATCH v2 2/2] VMCI: Remove VMCI_HANDLE_ARRAY_HEADER_SIZE and VMCI_HANDLE_ARRAY_MAX_CAPACITY

[Christophe JAILLET]

Remove VMCI_HANDLE_ARRAY_HEADER_SIZE and VMCI_HANDLE_ARRAY_MAX_CAPACITY
that are unused.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
Changes in v2:
   - no change in code
   - add R-b

v1: https://lore.kernel.org/all/c2a231a5ea127b28b5d8c4e86ef471dd01069d47.1702068153.git.christophe.jaillet@wanadoo.fr/
---
 drivers/misc/vmw_vmci/vmci_handle_array.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/misc/vmw_vmci/vmci_handle_array.h b/drivers/misc/vmw_vmci/vmci_handle_array.h
index b0e6b1956014..27a38b97e8a8 100644
--- a/drivers/misc/vmw_vmci/vmci_handle_array.h
+++ b/drivers/misc/vmw_vmci/vmci_handle_array.h
@@ -20,14 +20,8 @@ struct vmci_handle_arr {
 	struct vmci_handle entries[] __counted_by(capacity);
 };
 
-#define VMCI_HANDLE_ARRAY_HEADER_SIZE				\
-	offsetof(struct vmci_handle_arr, entries)
 /* Select a default capacity that results in a 64 byte sized array */
 #define VMCI_HANDLE_ARRAY_DEFAULT_CAPACITY			6
-/* Make sure that the max array size can be expressed by a u32 */
-#define VMCI_HANDLE_ARRAY_MAX_CAPACITY				\
-	((U32_MAX - VMCI_HANDLE_ARRAY_HEADER_SIZE - 1) /	\
-	sizeof(struct vmci_handle))
 
 struct vmci_handle_arr *vmci_handle_arr_create(u32 capacity, u32 max_capacity);
 void vmci_handle_arr_destroy(struct vmci_handle_arr *array);
-- 
2.34.1

Re: [PATCH v2 1/2] VMCI: Remove handle_arr_calc_size()

[Kees Cook]

On Sat, Dec 09, 2023 at 01:36:14PM +0100, Christophe JAILLET wrote:
> Use struct_size() instead of handle_arr_calc_size().
> This is much more conventional.
> 
> While at it, use size_add() when computing the needed size in
> vmci_handle_arr_append_entry(). This prevents from (unlikely) overflow
> when computing the new size to reallocate.
> 
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook