On Wed, Sep 23, 2026 at 1:02 AM Gustavo A. R. Silva <[email protected]> wrote: > On 9/23/26 16:23, Kees Cook wrote: > > On Wed, Sep 23, 2026 at 03:10:08PM +0900, Gustavo A. R. Silva wrote: > >> > >> > >> On 9/23/26 14:53, Bill Wendling wrote: > >>> Add the "__counted_by_ptr" attribute to the buffer field of "struct > >>> vmbus_gpadl". This allows compilers (GCC and Clang) to perform > >>> compile-time and runtime bounds-checking when KASAN is enabled, preventing > >>> potential out-of-bounds accesses to the GPADL buffer. > >>> > >>> The fields "buffer" and "size" of "struct vmbus_gpadl" are assigned > >>> exactly once, during GPADL establishment inside > >>> "__vmbus_establish_gpadl()" in "drivers/hv/channel.c". > >>> > >>> To ensure that the count field ("size") is initialized before the > >>> pointer field ("buffer") is assigned, we reorder the assignments in > >>> "__vmbus_establish_gpadl()" so that "gpadl->size" is written before > >>> "gpadl->buffer". > >>> > >>> Cc: [email protected] > >>> Assisted-by: LLM > >>> Signed-off-by: Bill Wendling <[email protected]> > >>> --- > >>> drivers/hv/channel.c | 2 +- > >>> include/linux/hyperv.h | 2 +- > >>> 2 files changed, 2 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c > >>> index 7e4cc6f55237..7042de2dd481 100644 > >>> --- a/drivers/hv/channel.c > >>> +++ b/drivers/hv/channel.c > >>> @@ -548,8 +548,8 @@ static int __vmbus_establish_gpadl(struct > >>> vmbus_channel *channel, > >>> /* At this point, we received the gpadl created msg */ > >>> gpadl->gpadl_handle = gpadlmsg->gpadl; > >>> - gpadl->buffer = kbuffer; > >>> gpadl->size = size; > >>> + gpadl->buffer = kbuffer; > >> > >> I think in some cases these subtle changes are worth a short but > >> informative comment saying that the _counter_ must be initialized > >> before the first reference to the pointer. > > > > But that's only for dereferencing it... there's no ordering requirement > > Ah yes, I got a bit carried away by the change itself. > > > here at all (and I think swapping order is needless churn). Neither > > order is correct: only having them both set before dereferencing > > "buffer" is required. > Yes; maybe this is something the LLM should learn. > > Thanks > -Gustavo
I've explicitly told the LLM exactly this, but it either forgets or ignores it. *sigh* -bw
