On Sat, Sep 23, 2023 at 2:53 AM Kees Cook <[email protected]> wrote: > > 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 checking via CONFIG_UBSAN_BOUNDS > (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family > functions). > > As found with Coccinelle[1], add __counted_by for struct cxl_cxims_data. > Additionally, since the element count member must be set before accessing > the annotated flexible array member, move its initialization earlier. > > [1] > https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci > > Cc: Davidlohr Bueso <[email protected]> > Cc: Jonathan Cameron <[email protected]> > Cc: Dave Jiang <[email protected]> > Cc: Alison Schofield <[email protected]> > Cc: Vishal Verma <[email protected]> > Cc: Ira Weiny <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: [email protected] > Signed-off-by: Kees Cook <[email protected]>
Looks good. The reordering of the count assignment is crucial here otherwise the runtime checks will trip when `cximsd->xormaps` is used as memcpy destination. Reviewed-by: Justin Stitt <[email protected]> > --- > drivers/cxl/acpi.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index d1c559879dcc..40d055560e52 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -14,7 +14,7 @@ > > struct cxl_cxims_data { > int nr_maps; > - u64 xormaps[]; > + u64 xormaps[] __counted_by(nr_maps); > }; > > /* > @@ -112,9 +112,9 @@ static int cxl_parse_cxims(union acpi_subtable_headers > *header, void *arg, > GFP_KERNEL); > if (!cximsd) > return -ENOMEM; > + cximsd->nr_maps = nr_maps; > memcpy(cximsd->xormaps, cxims->xormap_list, > nr_maps * sizeof(*cximsd->xormaps)); > - cximsd->nr_maps = nr_maps; > cxlrd->platform_data = cximsd; > > return 0; > -- > 2.34.1 > >
