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Message-ID: <ZJIXdfbEVfLliPov@work>
Date: Tue, 20 Jun 2023 15:17:41 -0600
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: M Chetan Kumar <m.chetan.kumar@...el.com>,
Florian Klink <flokli@...kli.de>,
Bagas Sanjaya <bagasdotme@...il.com>,
Intel Corporation <linuxwwan@...el.com>,
Loic Poulain <loic.poulain@...aro.org>,
Sergey Ryazanov <ryazanov.s.a@...il.com>,
Johannes Berg <johannes@...solutions.net>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] net: wwan: iosm: Convert single instance struct member
to flexible array
On Tue, Jun 20, 2023 at 12:42:38PM -0700, Kees Cook wrote:
> struct mux_adth actually ends with multiple struct mux_adth_dg members.
> This is seen both in the comments about the member:
>
> /**
> * struct mux_adth - Structure of the Aggregated Datagram Table Header.
> ...
> * @dg: datagramm table with variable length
> */
>
> and in the preparation for populating it:
>
> adth_dg_size = offsetof(struct mux_adth, dg) +
> ul_adb->dg_count[i] * sizeof(*dg);
> ...
> adth_dg_size -= offsetof(struct mux_adth, dg);
> memcpy(&adth->dg, ul_adb->dg[i], adth_dg_size);
>
> This was reported as a run-time false positive warning:
>
> memcpy: detected field-spanning write (size 16) of single field "&adth->dg" at drivers/net/wwan/iosm/iosm_ipc_mux_codec.c:852 (size 8)
>
> Adjust the struct mux_adth definition and associated sizeof() math; no binary
> output differences are observed in the resulting object file.
>
> Reported-by: Florian Klink <flokli@...kli.de>
> Closes: https://lore.kernel.org/lkml/dbfa25f5-64c8-5574-4f5d-0151ba95d232@gmail.com/
> Fixes: 1f52d7b62285 ("net: wwan: iosm: Enable M.2 7360 WWAN card support")
> Cc: M Chetan Kumar <m.chetan.kumar@...el.com>
> Cc: Bagas Sanjaya <bagasdotme@...il.com>
> Cc: Intel Corporation <linuxwwan@...el.com>
> Cc: Loic Poulain <loic.poulain@...aro.org>
> Cc: Sergey Ryazanov <ryazanov.s.a@...il.com>
> Cc: Johannes Berg <johannes@...solutions.net>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Thank god they used offsetof(struct mux_adth, dg) everywhere. :P
--
Gustavo
> ---
> drivers/net/wwan/iosm/iosm_ipc_mux_codec.c | 15 ++++++---------
> drivers/net/wwan/iosm/iosm_ipc_mux_codec.h | 2 +-
> 2 files changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> index d6b166fc5c0e..bff46f7ca59f 100644
> --- a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> +++ b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.c
> @@ -626,14 +626,12 @@ static void mux_dl_adb_decode(struct iosm_mux *ipc_mux,
> if (adth->signature != cpu_to_le32(IOSM_AGGR_MUX_SIG_ADTH))
> goto adb_decode_err;
>
> - if (le16_to_cpu(adth->table_length) < (sizeof(struct mux_adth) -
> - sizeof(struct mux_adth_dg)))
> + if (le16_to_cpu(adth->table_length) < sizeof(struct mux_adth))
> goto adb_decode_err;
>
> /* Calculate the number of datagrams. */
> nr_of_dg = (le16_to_cpu(adth->table_length) -
> - sizeof(struct mux_adth) +
> - sizeof(struct mux_adth_dg)) /
> + sizeof(struct mux_adth)) /
> sizeof(struct mux_adth_dg);
>
> /* Is the datagram table empty ? */
> @@ -649,7 +647,7 @@ static void mux_dl_adb_decode(struct iosm_mux *ipc_mux,
> }
>
> /* New aggregated datagram table. */
> - dg = &adth->dg;
> + dg = adth->dg;
> if (mux_dl_process_dg(ipc_mux, adbh, dg, skb, if_id,
> nr_of_dg) < 0)
> goto adb_decode_err;
> @@ -849,7 +847,7 @@ static void ipc_mux_ul_encode_adth(struct iosm_mux *ipc_mux,
> adth->if_id = i;
> adth->table_length = cpu_to_le16(adth_dg_size);
> adth_dg_size -= offsetof(struct mux_adth, dg);
> - memcpy(&adth->dg, ul_adb->dg[i], adth_dg_size);
> + memcpy(adth->dg, ul_adb->dg[i], adth_dg_size);
> ul_adb->if_cnt++;
> }
>
> @@ -1426,14 +1424,13 @@ static int ipc_mux_get_payload_from_adb(struct iosm_mux *ipc_mux,
>
> if (adth->signature == cpu_to_le32(IOSM_AGGR_MUX_SIG_ADTH)) {
> nr_of_dg = (le16_to_cpu(adth->table_length) -
> - sizeof(struct mux_adth) +
> - sizeof(struct mux_adth_dg)) /
> + sizeof(struct mux_adth)) /
> sizeof(struct mux_adth_dg);
>
> if (nr_of_dg <= 0)
> return payload_size;
>
> - dg = &adth->dg;
> + dg = adth->dg;
>
> for (i = 0; i < nr_of_dg; i++, dg++) {
> if (le32_to_cpu(dg->datagram_index) <
> diff --git a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.h b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.h
> index 5d4e3b89542c..f8df88f816c4 100644
> --- a/drivers/net/wwan/iosm/iosm_ipc_mux_codec.h
> +++ b/drivers/net/wwan/iosm/iosm_ipc_mux_codec.h
> @@ -161,7 +161,7 @@ struct mux_adth {
> u8 opt_ipv4v6;
> __le32 next_table_index;
> __le32 reserved2;
> - struct mux_adth_dg dg;
> + struct mux_adth_dg dg[];
> };
>
> /**
> --
> 2.34.1
>
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