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.schauf...@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),
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