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Message-ID: <202310091503.E59363D14@keescook> Date: Mon, 9 Oct 2023 15:03:56 -0700 From: Kees Cook <keescook@...omium.org> To: "Gustavo A. R. Silva" <gustavoars@...nel.org> Cc: Lars-Peter Clausen <lars@...afoo.de>, Nuno Sá <nuno.sa@...log.com>, Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH][next] ASoC: sigmadsp: Add __counted_by for struct sigmadsp_data and use struct_size() 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 <gustavoars@...nel.org> > --- > 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 <keescook@...omium.org> -- Kees Cook
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