linux-hardening - RE: [PATCH v2 43/63] net: qede: Use memset

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Date:   Tue, 24 Aug 2021 16:51:55 +0000
From:   Shai Malin <smalin@...vell.com>
To:     Kees Cook <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Ariel Elior <aelior@...vell.com>,
        GR-everest-linux-l2 <GR-everest-linux-l2@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kbuild@...r.kernel.org" <linux-kbuild@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: RE: [PATCH v2 43/63] net: qede: Use memset_startat() for counters

On August 18, 2021 9:05 AM -0300, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
> 
> Use memset_startat() so memset() doesn't get confused about writing
> beyond the destination member that is intended to be the starting point
> of zeroing through the end of the struct.
> 
> The old code was doing the wrong thing: it starts from the second member
> and writes beyond int_info, clobbering qede_lock:
> 
> struct qede_dev {
> 	...
>         struct qed_int_info             int_info;
> 
>         /* Smaller private variant of the RTNL lock */
>         struct mutex                    qede_lock;
> 	...
> 
> struct qed_int_info {
>         struct msix_entry       *msix;
>         u8                      msix_cnt;
> 
>         /* This should be updated by the protocol driver */
>         u8                      used_cnt;
> };
> 
> Cc: Ariel Elior <aelior@...vell.com>
> Cc: GR-everest-linux-l2@...vell.com
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/net/ethernet/qlogic/qede/qede_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/qlogic/qede/qede_main.c
> b/drivers/net/ethernet/qlogic/qede/qede_main.c
> index d400e9b235bf..0ed9a0c8452c 100644
> --- a/drivers/net/ethernet/qlogic/qede/qede_main.c
> +++ b/drivers/net/ethernet/qlogic/qede/qede_main.c
> @@ -2419,7 +2419,7 @@ static int qede_load(struct qede_dev *edev, enum
> qede_load_mode mode,
>  	goto out;
>  err4:
>  	qede_sync_free_irqs(edev);
> -	memset(&edev->int_info.msix_cnt, 0, sizeof(struct qed_int_info));
> +	memset_startat(&edev->int_info, 0, msix_cnt);

As I commented on V1:
"[PATCH 42/64] net: qede: Use memset_after() for counters",
the memset is redundant and it should clear only the msix_cnt.

We will fix it.

>  err3:
>  	qede_napi_disable_remove(edev);
>  err2:
> --
> 2.30.2