From: Stephen Smalley <sds@tycho.nsa.gov>
To: Casey Schaufler <casey.schaufler@intel.com>,
kernel-hardening@lists.openwall.com,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov,
SMACK-discuss@lists.01.org, dave.hansen@intel.com,
deneen.t.dock@intel.com, kristen@linux.intel.com,
arjan@linux.intel.com
Subject: Re: [PATCH RFC 5/5] SELinux: Support SELinux determination of side-channel vulnerability
Date: Thu, 16 Aug 2018 10:12:58 -0400 [thread overview]
Message-ID: <0b383282-1369-79e9-d111-f03e2897660e@tycho.nsa.gov> (raw)
In-Reply-To: <20180815235355.14908-6-casey.schaufler@intel.com>
On 08/15/2018 07:53 PM, Casey Schaufler wrote:
> SELinux considers tasks to be side-channel safe if they
> have PROCESS_SHARE access.
>
> Signed-off-by: Casey Schaufler <casey.schaufler@intel.com>
> ---
> security/selinux/hooks.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a8bf324130f5..7fbd7d7ac1cb 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4219,6 +4219,14 @@ static void selinux_task_to_inode(struct task_struct *p,
> spin_unlock(&isec->lock);
> }
>
> +static int selinux_task_safe_sidechannel(struct task_struct *p)
> +{
> + struct av_decision avd;
> +
> + return avc_has_perm_noaudit(&selinux_state, current_sid(), task_sid(p),
> + SECCLASS_PROCESS, PROCESS__SHARE, 0, &avd);
> +}
If you are going to apply this kind of check, is there a reason you
wouldn't just use the ptrace checking logic? Just call
ptrace_may_access() with PTRACE_MODE_READ and dispense with having a
separate hook altogether. Then you get uids/gids, caps, dumpable, and
security module checking for free.
Regardless, I don't think share permission is the right answer here; it
has very different semantics and security implications, and is almost
never allowed in Android policy (just one instance for kernel->init
transition).
> +
> /* Returns error only if unable to parse addresses */
> static int selinux_parse_skb_ipv4(struct sk_buff *skb,
> struct common_audit_data *ad, u8 *proto)
> @@ -7002,6 +7010,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(task_movememory, selinux_task_movememory),
> LSM_HOOK_INIT(task_kill, selinux_task_kill),
> LSM_HOOK_INIT(task_to_inode, selinux_task_to_inode),
> + LSM_HOOK_INIT(task_safe_sidechannel, selinux_task_safe_sidechannel),
>
> LSM_HOOK_INIT(ipc_permission, selinux_ipc_permission),
> LSM_HOOK_INIT(ipc_getsecid, selinux_ipc_getsecid),
>
next prev parent reply other threads:[~2018-08-16 14:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-15 23:53 [PATCH RFC 0/5] LSM: Add and use a hook for side-channel safety checks Casey Schaufler
2018-08-15 23:53 ` [PATCH RFC 1/5] LSM: Introduce a hook for side-channel danger Casey Schaufler
2018-08-15 23:53 ` [PATCH RFC 2/5] X86: Support LSM determination of side-channel vulnerability Casey Schaufler
2018-08-16 14:09 ` Jann Horn
2018-08-15 23:53 ` [PATCH RFC 3/5] LSM: Security module checking for side-channel dangers Casey Schaufler
2018-08-16 14:15 ` Jann Horn
2018-08-15 23:53 ` [PATCH RFC 4/5] Smack: Support determination of side-channel vulnerability Casey Schaufler
2018-08-15 23:53 ` [PATCH RFC 5/5] SELinux: Support SELinux " Casey Schaufler
2018-08-16 14:12 ` Stephen Smalley [this message]
2018-08-16 14:22 ` Jann Horn
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