From: Kees Cook <keescook@chromium.org>
To: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Peter Huewe <peterhuewe@gmx.de>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: Re: [PATCH RESEND] tpm: eventlog: Replace zero-length array with flexible-array member
Date: Thu, 7 May 2020 11:02:18 -0700 [thread overview]
Message-ID: <202005071058.A2234694ED@keescook> (raw)
In-Reply-To: <20200507040912.GA31382@embeddedor>
On Wed, May 06, 2020 at 11:09:12PM -0500, Gustavo A. R. Silva wrote:
> As mentioned above: "Flexible array members have incomplete type, and
> so the sizeof operator may not be applied. As a quirk of the original
> implementation of zero-length arrays, sizeof evaluates to zero."[1] So,
> the sizeof(flexible-array) can be safely removed to fix the error above.
As in "sizeof(event_header->event) always evaluated to 0, so removing it
has no effect".
> [...]
> diff --git a/drivers/char/tpm/eventlog/tpm2.c b/drivers/char/tpm/eventlog/tpm2.c
> index e741b1157525..351a2989b3c6 100644
> --- a/drivers/char/tpm/eventlog/tpm2.c
> +++ b/drivers/char/tpm/eventlog/tpm2.c
> @@ -51,8 +51,7 @@ static void *tpm2_bios_measurements_start(struct seq_file *m, loff_t *pos)
> int i;
>
> event_header = addr;
> - size = sizeof(struct tcg_pcr_event) - sizeof(event_header->event)
> - + event_header->event_size;
> + size = sizeof(*event_header) + event_header->event_size;
That said, I think it would be better to stick to the struct_size()
idiom for dealing with flexible arrays here:
size = struct_size(event_header, event, event_size);
--
Kees Cook
next prev parent reply other threads:[~2020-05-07 18:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 4:09 [PATCH RESEND] tpm: eventlog: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-05-07 18:02 ` Kees Cook [this message]
2020-05-08 16:06 ` Gustavo A. R. Silva
2020-05-13 21:39 ` Jarkko Sakkinen
2020-05-13 23:14 ` Gustavo A. R. Silva
2020-05-14 11:05 ` Jarkko Sakkinen
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