Fake flexible arrays (zero-length and one-element arrays) are deprecated,
and should be replaced by flexible-array members. So, replace
zero-length array with a flexible-array member in `struct
privcmd_kernel_ioreq`.
Also annotate array `ports` with `__counted_by()` to prepare for the
coming implementation by GCC and Clang of the `__counted_by` attribute.
Flexible array members annotated with `__counted_by` can have their
accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
This fixes multiple -Warray-bounds warnings:
drivers/xen/privcmd.c:1239:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
drivers/xen/privcmd.c:1240:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
drivers/xen/privcmd.c:1241:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
drivers/xen/privcmd.c:1245:33: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
drivers/xen/privcmd.c:1258:67: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
This results in no differences in binary output.
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/xen/privcmd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 1ce7f3c7a950..0eb337a8ec0f 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -1115,7 +1115,7 @@ struct privcmd_kernel_ioreq {
spinlock_t lock; /* Protects ioeventfds list */
struct list_head ioeventfds;
struct list_head list;
- struct ioreq_port ports[0];
+ struct ioreq_port ports[] __counted_by(vcpus);
};
static irqreturn_t ioeventfd_interrupt(int irq, void *dev_id)
--
2.34.1
On Thu, Nov 16, 2023 at 12:54:59PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> privcmd_kernel_ioreq`.
>
> Also annotate array `ports` with `__counted_by()` to prepare for the
> coming implementation by GCC and Clang of the `__counted_by` attribute.
> Flexible array members annotated with `__counted_by` can have their
> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
>
> This fixes multiple -Warray-bounds warnings:
> drivers/xen/privcmd.c:1239:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1240:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1241:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1245:33: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1258:67: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>
> This results in no differences in binary output.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
Looks right to me. I can see the allocation:
size = struct_size(kioreq, ports, ioeventfd->vcpus);
kioreq = kzalloc(size, GFP_KERNEL);
if (!kioreq)
return ERR_PTR(-ENOMEM);
kioreq->dom = ioeventfd->dom;
kioreq->vcpus = ioeventfd->vcpus;
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
On 11/16/23 15:08, Kees Cook wrote:
> On Thu, Nov 16, 2023 at 12:54:59PM -0600, Gustavo A. R. Silva wrote:
>> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
>> and should be replaced by flexible-array members. So, replace
>> zero-length array with a flexible-array member in `struct
>> privcmd_kernel_ioreq`.
>>
>> Also annotate array `ports` with `__counted_by()` to prepare for the
>> coming implementation by GCC and Clang of the `__counted_by` attribute.
>> Flexible array members annotated with `__counted_by` can have their
>> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
>> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
>>
>> This fixes multiple -Warray-bounds warnings:
>> drivers/xen/privcmd.c:1239:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>> drivers/xen/privcmd.c:1240:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>> drivers/xen/privcmd.c:1241:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>> drivers/xen/privcmd.c:1245:33: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>> drivers/xen/privcmd.c:1258:67: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>>
>> This results in no differences in binary output.
>>
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>
> Looks right to me. I can see the allocation:
Yep, I always check for that; in particular, the 'counter' assignment. :)
Do you want me to mention it in the changelog text?
>
> size = struct_size(kioreq, ports, ioeventfd->vcpus);
> kioreq = kzalloc(size, GFP_KERNEL);
> if (!kioreq)
> return ERR_PTR(-ENOMEM);
>
> kioreq->dom = ioeventfd->dom;
> kioreq->vcpus = ioeventfd->vcpus;
>
>
> Reviewed-by: Kees Cook <[email protected]>
Thanks!
--
Gustavo
On 16.11.23 19:54, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> privcmd_kernel_ioreq`.
>
> Also annotate array `ports` with `__counted_by()` to prepare for the
> coming implementation by GCC and Clang of the `__counted_by` attribute.
> Flexible array members annotated with `__counted_by` can have their
> accesses bounds-checked at run-time via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
>
> This fixes multiple -Warray-bounds warnings:
> drivers/xen/privcmd.c:1239:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1240:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1241:30: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1245:33: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
> drivers/xen/privcmd.c:1258:67: warning: array subscript i is outside array bounds of 'struct ioreq_port[0]' [-Warray-bounds=]
>
> This results in no differences in binary output.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
Reviewed-by: Juergen Gross <[email protected]>
Juergen