From 10cfde5dc695856c4fe93f0679d2fdd8e0d2a147 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 20 Jul 2020 10:31:19 -0700 Subject: [PATCH] ACPICA: Replace one-element array with flexible-array ACPICA commit 7ba2f3d91a32f104765961fda0ed78b884ae193d The current codebase makes use of one-element arrays in the following form: struct something { int length; u8 data[1]; }; struct something *instance; instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size); but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the linux codebase from now on. This issue was found with the help of Coccinelle and audited _manually_. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Link: https://github.com/acpica/acpica/commit/7ba2f3d9 Signed-off-by: Gustavo A. R. Silva Signed-off-by: Erik Kaneda Signed-off-by: Bob Moore Signed-off-by: Rafael J. Wysocki --- drivers/acpi/acpica/utids.c | 3 +-- include/acpi/actypes.h | 2 +- 2 files changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c index 3bb06935a2ad..3e68864ef242 100644 --- a/drivers/acpi/acpica/utids.c +++ b/drivers/acpi/acpica/utids.c @@ -263,8 +263,7 @@ acpi_ut_execute_CID(struct acpi_namespace_node *device_node, * 3) Size of the actual CID strings */ cid_list_size = sizeof(struct acpi_pnp_device_id_list) + - ((count - 1) * sizeof(struct acpi_pnp_device_id)) + - string_area_size; + (count * sizeof(struct acpi_pnp_device_id)) + string_area_size; cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size); if (!cid_list) { diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h index aa236b9e6f24..735921c833f8 100644 --- a/include/acpi/actypes.h +++ b/include/acpi/actypes.h @@ -1146,7 +1146,7 @@ struct acpi_pnp_device_id { struct acpi_pnp_device_id_list { u32 count; /* Number of IDs in Ids array */ u32 list_size; /* Size of list, including ID strings */ - struct acpi_pnp_device_id ids[1]; /* ID array */ + struct acpi_pnp_device_id ids[]; /* ID array */ }; /*