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Date: Mon, 19 Sep 2011 21:39:05 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Balbir Singh <bsingharora@...il.com>, Shailabh Nagar <nagar@...ibm.com>,
linux-kernel@...r.kernel.org, security@...nel.org,
Eric Paris <eparis@...hat.com>, Stephen Wilson <wilsons@...rt.ca>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
David Rientjes <rientjes@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
kernel-hardening@...ts.openwall.com
Subject: Re: [Security] [PATCH 2/2] taskstats: restrict access to user
On Mon, Sep 19, 2011 at 09:40 -0700, Linus Torvalds wrote:
> diff --git a/kernel/taskstats.c b/kernel/taskstats.c
> index e19ce1454ee1..5874d4866b3c 100644
> --- a/kernel/taskstats.c
> +++ b/kernel/taskstats.c
> @@ -457,6 +457,8 @@ static int cmd_attr_register_cpumask(struct genl_info *info)
> cpumask_var_t mask;
> int rc;
>
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
Shouldn't it simply protect taskstats_user_cmd()? You may still poll
the counters with TASKSTATS_CMD_ATTR_PID/TASKSTATS_CMD_ATTR_TGID.
Or ptrace_may_access() in taskstats_user_cmd().
> if (!alloc_cpumask_var(&mask, GFP_KERNEL))
> return -ENOMEM;
> rc = parse(info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK], mask);
> diff --git a/kernel/tsacct.c b/kernel/tsacct.c
> index 24dc60d9fa1f..110ca5a03bd6 100644
> --- a/kernel/tsacct.c
> +++ b/kernel/tsacct.c
> @@ -78,6 +78,7 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
>
> #define KB 1024
> #define MB (1024*KB)
> +#define KB_MASK (~(KB-1))
> /*
> * fill in extended accounting fields
> */
> @@ -100,9 +101,9 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
> stats->read_syscalls = p->ioac.syscr;
> stats->write_syscalls = p->ioac.syscw;
> #ifdef CONFIG_TASK_IO_ACCOUNTING
> - stats->read_bytes = p->ioac.read_bytes;
> - stats->write_bytes = p->ioac.write_bytes;
> - stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes;
> + stats->read_bytes = p->ioac.read_bytes & KB_MASK;
> + stats->write_bytes = p->ioac.write_bytes & KB_MASK;
> + stats->cancelled_write_bytes = p->ioac.cancelled_write_bytes & KB_MASK;
> #else
> stats->read_bytes = 0;
> stats->write_bytes = 0;
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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