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Message-ID: <20120331044030.GB3077@pinguin>
Date: Sat, 31 Mar 2012 08:40:33 +0400
From: Vladimir Murzin <murzin.v@...il.com>
To: Will Drewry <wad@...omium.org>
Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
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Subject: Re: [PATCH v17 08/15] seccomp: add system call filtering using BPF
Hi Will,
On Thu, Mar 29, 2012 at 03:01:53PM -0500, Will Drewry wrote:
snipped
> +
> +/* Limit any path through the tree to 256KB worth of instructions. */
> +#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
> +
> +static void seccomp_filter_log_failure(int syscall)
> +{
> + int compat = 0;
> +#ifdef CONFIG_COMPAT
> + compat = is_compat_task();
> +#endif
> + pr_info("%s[%d]: %ssystem call %d blocked at 0x%lx\n",
> + current->comm, task_pid_nr(current),
> + (compat ? "compat " : ""),
> + syscall, KSTK_EIP(current));
> +}
snipped
> +/**
> + * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
> + * @user_filter: pointer to the user data containing a sock_fprog.
> + *
> + * Returns 0 on success and non-zero otherwise.
> + */
> +long seccomp_attach_user_filter(char __user *user_filter)
> +{
> + struct sock_fprog fprog;
> + long ret = -EFAULT;
> +
> +#ifdef CONFIG_COMPAT
> + if (is_compat_task()) {
> + struct compat_sock_fprog fprog32;
> + if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
> + goto out;
> + fprog.len = fprog32.len;
> + fprog.filter = compat_ptr(fprog32.filter);
> + } else /* falls through to the if below. */
> +#endif
> + if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
> + goto out;
> + ret = seccomp_attach_filter(&fprog);
> +out:
> + return ret;
> +}
Do we really need to surround is_compat_task() with CNFIG_COMPAT?
It seems that this case has already handled in compat.h [1]
[1] http://lxr.linux.no/#linux+v3.3/include/linux/compat.h#L566
Best wishes
Vladimir Murzin
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