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 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")
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
Changes in v2:
- Don't use struct_size() for now.
- Update subject line and changelog text.
drivers/acpi/acpica/utids.c | 2 +-
include/acpi/actypes.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/acpica/utids.c b/drivers/acpi/acpica/utids.c
index 3bb06935a2ad3..225f3c60203c7 100644
--- a/drivers/acpi/acpica/utids.c
+++ b/drivers/acpi/acpica/utids.c
@@ -263,7 +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)) +
+ count * sizeof(struct acpi_pnp_device_id) +
string_area_size;
cid_list = ACPI_ALLOCATE_ZEROED(cid_list_size);
diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 4defed58ea338..c7bcda0ad366a 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -1145,7 +1145,7 @@ 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 */
};
/*
--
2.27.0
