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Re: [PATCH][next] xen: privcmd: Replace zero-length array with flex-array member and use __counted_by
- To: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Fri, 17 Nov 2023 08:24:44 +0100
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-hardening@xxxxxxxxxxxxxxx
- Delivery-date: Fri, 17 Nov 2023 07:25:00 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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 <gustavoars@xxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Juergen
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