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Replace one-element array with flexible-array 

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")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
This commit is contained in:
Gustavo A. R. Silva 2020-06-02 23:34:00 -07:00 committed by Erik Kaneda
parent cb73949edc
commit 7ba2f3d91a
2 changed files with 2 additions and 2 deletions
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2
source/components/utilities/utids.c
View File

@ -435,7 +435,7 @@ AcpiUtExecute_CID (
* 3) Size of the actual CID strings
*/
CidListSize = sizeof (ACPI_PNP_DEVICE_ID_LIST) +
((Count - 1) * sizeof (ACPI_PNP_DEVICE_ID)) +
(Count * sizeof (ACPI_PNP_DEVICE_ID)) +
StringAreaSize;
CidList = ACPI_ALLOCATE_ZEROED (CidListSize);

2
source/include/actypes.h
View File

@ -1379,7 +1379,7 @@ typedef struct acpi_pnp_device_id_list
{
UINT32 Count; /* Number of IDs in Ids array */
UINT32 ListSize; /* Size of list, including ID strings */
ACPI_PNP_DEVICE_ID Ids[1]; /* ID array */
ACPI_PNP_DEVICE_ID Ids[]; /* ID array */
} ACPI_PNP_DEVICE_ID_LIST;