linux-kernel - Re: [PATCH 1/2] security: let security modules use PTRACE_MODE

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Message-ID: <5665FF76.5090701@schaufler-ca.com>
Date:	Mon, 7 Dec 2015 13:51:50 -0800
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Jann Horn <jann@...jh.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...gle.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Joe Perches <joe@...ches.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-security-module@...r.kernel.org, linux-api@...r.kernel.org,
	security@...nel.org, Willy Tarreau <w@....eu>
Subject: Re: [PATCH 1/2] security: let security modules use PTRACE_MODE_* with
 bitmasks

On 12/7/2015 1:25 PM, Jann Horn wrote:
> It looks like smack and yama weren't aware that the ptrace mode
> can have flags ORed into it - PTRACE_MODE_NOAUDIT until now, but
> only for /proc/$pid/stat, and with the PTRACE_MODE_*CREDS patch,
> all modes have flags ORed into them.
>
> Signed-off-by: Jann Horn <jann@...jh.net>

Acked-by: Casey Schaufler <casey@...aufler-ca.com>

> ---
>   security/smack/smack_lsm.c | 8 +++-----
>   security/yama/yama_lsm.c   | 4 ++--
>   2 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index ff81026..7c57c7f 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -398,12 +398,10 @@ static int smk_copy_relabel(struct list_head *nhead, struct list_head *ohead,
>    */
>   static inline unsigned int smk_ptrace_mode(unsigned int mode)
>   {
> -	switch (mode) {
> -	case PTRACE_MODE_READ:
> -		return MAY_READ;
> -	case PTRACE_MODE_ATTACH:
> +	if (mode & PTRACE_MODE_ATTACH)
>   		return MAY_READWRITE;
> -	}
> +	if (mode & PTRACE_MODE_READ)
> +		return MAY_READ;
>   
>   	return 0;
>   }
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index d3c19c9..cb6ed10 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -281,7 +281,7 @@ static int yama_ptrace_access_check(struct task_struct *child,
>   	int rc = 0;
>   
>   	/* require ptrace target be a child of ptracer on attach */
> -	if (mode == PTRACE_MODE_ATTACH) {
> +	if (mode & PTRACE_MODE_ATTACH) {
>   		switch (ptrace_scope) {
>   		case YAMA_SCOPE_DISABLED:
>   			/* No additional restrictions. */
> @@ -307,7 +307,7 @@ static int yama_ptrace_access_check(struct task_struct *child,
>   		}
>   	}
>   
> -	if (rc) {
> +	if (rc && (mode & PTRACE_MODE_NOAUDIT) == 0) {
>   		printk_ratelimited(KERN_NOTICE
>   			"ptrace of pid %d was attempted by: %s (pid %d)\n",
>   			child->pid, current->comm, current->pid);

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