linux-kernel - Re: [PATCH v2 1/2] samples, selftests/seccomp: Zero out seccomp

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Date:   Sat, 28 Dec 2019 11:18:25 -0700
From:   Tycho Andersen <tycho@...ho.ws>
To:     Sargun Dhillon <sargun@...gun.me>
Cc:     linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        jannh@...gle.com, christian.brauner@...ntu.com,
        keescook@...omium.org, cyphar@...har.com
Subject: Re: [PATCH v2 1/2] samples, selftests/seccomp: Zero out seccomp_notif

On Sat, Dec 28, 2019 at 01:48:39AM +0000, Sargun Dhillon wrote:
> The seccomp_notif structure should be zeroed out prior to calling the
> SECCOMP_IOCTL_NOTIF_RECV ioctl. Previously, the kernel did not check
> whether these structures were zeroed out or not, so these worked.
> 
> Signed-off-by: Sargun Dhillon <sargun@...gun.me>
> Cc: Kees Cook <keescook@...omium.org>
> ---
>  samples/seccomp/user-trap.c                   | 2 +-
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/samples/seccomp/user-trap.c b/samples/seccomp/user-trap.c
> index 6d0125ca8af7..0ca8fb37cd79 100644
> --- a/samples/seccomp/user-trap.c
> +++ b/samples/seccomp/user-trap.c
> @@ -298,7 +298,6 @@ int main(void)
>  		req = malloc(sizes.seccomp_notif);
>  		if (!req)
>  			goto out_close;
> -		memset(req, 0, sizeof(*req));
>  
>  		resp = malloc(sizes.seccomp_notif_resp);
>  		if (!resp)
> @@ -306,6 +305,7 @@ int main(void)
>  		memset(resp, 0, sizeof(*resp));

I know it's unrelated, but it's probably worth sending a patch to fix
this to be sizes.seccomp_notif_resp instead of sizeof(*resp), since if
the kernel is older this will over-zero things. I can do that, or you
can add the patch to this series, just let me know which.

But in any case, this patch is:

Reviewed-by: Tycho Andersen <tycho@...ho.ws>

Cheers,

Tycho