| Message ID | ZVZlg3tPMPCRdteh@work (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 295b202227e98edb2fb5cc29b6ec4b96b2792d9c |
| Headers | show |
| Series | [next] xen: privcmd: Replace zero-length array with flex-array member and use __counted_by | expand |
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 <gustavoars@kernel.org> 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 <keescook@chromium.org>
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 <gustavoars@kernel.org> > > 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 <keescook@chromium.org> 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 <gustavoars@kernel.org> Reviewed-by: Juergen Gross <jgross@suse.com> Juergen
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)
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@kernel.org> --- drivers/xen/privcmd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)