linux-kernel - Re: [RFC] [PATCH] audit: log 32-bit socketcalls

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Date:   Thu, 12 Jan 2017 16:32:44 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-audit@...hat.com
Subject: Re: [RFC] [PATCH] audit: log 32-bit socketcalls

On Thu, Jan 12, 2017 at 7:36 AM, Richard Guy Briggs <rgb@...hat.com> wrote:
> 32-bit socketcalls were not being logged by audit on x86_64 systems.
> Log them.
>
> See: https://github.com/linux-audit/audit-kernel/issues/14
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  net/compat.c |   18 ++++++++++++++++--
>  1 files changed, 16 insertions(+), 2 deletions(-)

You should CC netdev on this patch; I'd also mention that you are
simply duplicating the normal socketcall() auditing in the compat
version (the only real difference being the argument size handling
workaround).

> diff --git a/net/compat.c b/net/compat.c
> index 1cd2ec0..86cacab 100644
> --- a/net/compat.c
> +++ b/net/compat.c
> @@ -22,6 +22,7 @@
>  #include <linux/filter.h>
>  #include <linux/compat.h>
>  #include <linux/security.h>
> +#include <linux/audit.h>
>  #include <linux/export.h>
>
>  #include <net/scm.h>
> @@ -781,14 +782,27 @@ COMPAT_SYSCALL_DEFINE5(recvmmsg, int, fd, struct compat_mmsghdr __user *, mmsg,
>
>  COMPAT_SYSCALL_DEFINE2(socketcall, int, call, u32 __user *, args)
>  {
> +       unsigned int len, i;
>         int ret;
> -       u32 a[6];
> +       u32 a[AUDITSC_ARGS];
> +       unsigned long aa[AUDITSC_ARGS];
>         u32 a0, a1;
>
>         if (call < SYS_SOCKET || call > SYS_SENDMMSG)
>                 return -EINVAL;
> -       if (copy_from_user(a, args, nas[call]))
> +       len = nas[call];
> +       if (len > sizeof(a))
> +               return -EINVAL;
> +
> +       if (copy_from_user(a, args, len))
>                 return -EFAULT;
> +
> +       for (i=0; i < len/sizeof(a[0]); i++)
> +               aa[i] = (unsigned long)a[i];

It will be interesting to see if you get push back on this loop
outside of audit_socketcall(); folks may want to see it wrapped up
inside a audit_socketcall_compat() (or similar) function so it isn't
needlessly called in a number of cases.  However, considering it is
compat code, and not the common case it may be okay.

> +       ret = audit_socketcall(len/sizeof(a[0]), aa);
> +       if (ret)
> +               return ret;
> +
>         a0 = a[0];
>         a1 = a[1];
>
> --
> 1.7.1

-- 
paul moore
www.paul-moore.com