On Mon, Oct 09, 2023 at 03:24:23PM -0600, Gustavo A. R. Silva 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 via CONFIG_UBSAN_BOUNDS (for > array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family > functions). > > While there, use struct_size() and size_sub() helpers, instead of the > open-coded version, to calculate the size for the allocation of the > whole flexible structure, including of course, the flexible-array > member. > > This code was found with the help of Coccinelle, and audited and > fixed manually. > > Signed-off-by: Gustavo A. R. Silva <[email protected]> > --- > sound/soc/codecs/sigmadsp.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/sound/soc/codecs/sigmadsp.c b/sound/soc/codecs/sigmadsp.c > index b93c078a8040..56546e2394ab 100644 > --- a/sound/soc/codecs/sigmadsp.c > +++ b/sound/soc/codecs/sigmadsp.c > @@ -43,7 +43,7 @@ struct sigmadsp_data { > uint32_t samplerates; > unsigned int addr; > unsigned int length; > - uint8_t data[]; > + uint8_t data[] __counted_by(length); > }; > > struct sigma_fw_chunk { > @@ -270,7 +270,7 @@ static int sigma_fw_load_data(struct sigmadsp *sigmadsp, > > length -= sizeof(*data_chunk); > > - data = kzalloc(sizeof(*data) + length, GFP_KERNEL); > + data = kzalloc(struct_size(data, data, length), GFP_KERNEL); > if (!data) > return -ENOMEM; > > @@ -413,7 +413,8 @@ static int process_sigma_action(struct sigmadsp *sigmadsp, > if (len < 3) > return -EINVAL; > > - data = kzalloc(sizeof(*data) + len - 2, GFP_KERNEL); > + data = kzalloc(struct_size(data, data, size_sub(len, 2)), > + GFP_KERNEL);
Since len was just size-checked before the alloc, size_sub() is a bit of overkill, but it's not technically wrong. :P Reviewed-by: Kees Cook <[email protected]> -- Kees Cook
