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Message-ID: <CAKf6xptEEHJAsrwh_oebK1_AMb+_tvLtiY8sP-Qk=Z9jXhVf7Q@mail.gmail.com>
Date: Mon, 9 Oct 2023 10:55:32 -0400
From: Jason Andryuk <jandryuk@...il.com>
To: Kees Cook <keescook@...omium.org>
Cc: Christian Lamparter <chunkeey@...glemail.com>,
Kalle Valo <kvalo@...nel.org>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-wireless@...r.kernel.org, linux-hardening@...r.kernel.org,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: Re: [PATCH] wifi: p54: Annotate struct p54_cal_database with __counted_by
Hi,
I randomly peeked at this patch. Unfortunately, I am not familiar
with the actual p54 code.
On Fri, Oct 6, 2023 at 4:17 PM Kees Cook <keescook@...omium.org> 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).
>
> As found with Coccinelle[1], add __counted_by for struct p54_cal_database.
>
> Cc: Christian Lamparter <chunkeey@...glemail.com>
> Cc: Kalle Valo <kvalo@...nel.org>
> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: linux-wireless@...r.kernel.org
> Cc: linux-hardening@...r.kernel.org
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> drivers/net/wireless/intersil/p54/p54.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/intersil/p54/p54.h b/drivers/net/wireless/intersil/p54/p54.h
> index 3356ea708d81..770e348d1f6c 100644
> --- a/drivers/net/wireless/intersil/p54/p54.h
> +++ b/drivers/net/wireless/intersil/p54/p54.h
> @@ -126,7 +126,7 @@ struct p54_cal_database {
> size_t entry_size;
> size_t offset;
> size_t len;
> - u8 data[];
> + u8 data[] __counted_by(entries);
This looks incorrect - I think you want __counted_by(len)? The
presence of entry_size made me suspicious.
> };
This is the function that creates struct p54_cal_database:
static struct p54_cal_database *p54_convert_db(struct pda_custom_wrapper *src,
size_t total_len)
{
struct p54_cal_database *dst;
size_t payload_len, entries, entry_size, offset;
payload_len = le16_to_cpu(src->len);
entries = le16_to_cpu(src->entries);
entry_size = le16_to_cpu(src->entry_size);
offset = le16_to_cpu(src->offset);
if (((entries * entry_size + offset) != payload_len) ||
(payload_len + sizeof(*src) != total_len))
return NULL;
dst = kmalloc(sizeof(*dst) + payload_len, GFP_KERNEL);
if (!dst)
return NULL;
dst->entries = entries;
dst->entry_size = entry_size;
dst->offset = offset;
dst->len = payload_len;
memcpy(dst->data, src->data, payload_len);
return dst;
}
You can see that kmalloc is performed with `sizeof(*dst) +
payload_len`, and payload_len is assigned to ->len.
I don't read Coccinelle, but, if this patch was auto-generated, I
wonder if the script has an error.
Regards,
Jason
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