security: Fix setting of PF_SUPERPRIV by __capable()
Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags
the target process if that is not the current process and it is trying to
change its own flags in a different way at the same time.
__capable() is using neither atomic ops nor locking to protect t->flags. This
patch removes __capable() and introduces has_capability() that doesn't set
PF_SUPERPRIV on the process being queried.
This patch further splits security_ptrace() in two:
(1) security_ptrace_may_access(). This passes judgement on whether one
process may access another only (PTRACE_MODE_ATTACH for ptrace() and
PTRACE_MODE_READ for /proc), and takes a pointer to the child process.
current is the parent.
(2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only,
and takes only a pointer to the parent process. current is the child.
In Smack and commoncap, this uses has_capability() to determine whether
the parent will be permitted to use PTRACE_ATTACH if normal checks fail.
This does not set PF_SUPERPRIV.
Two of the instances of __capable() actually only act on current, and so have
been changed to calls to capable().
Of the places that were using __capable():
(1) The OOM killer calls __capable() thrice when weighing the killability of a
process. All of these now use has_capability().
(2) cap_ptrace() and smack_ptrace() were using __capable() to check to see
whether the parent was allowed to trace any process. As mentioned above,
these have been split. For PTRACE_ATTACH and /proc, capable() is now
used, and for PTRACE_TRACEME, has_capability() is used.
(3) cap_safe_nice() only ever saw current, so now uses capable().
(4) smack_setprocattr() rejected accesses to tasks other than current just
after calling __capable(), so the order of these two tests have been
switched and capable() is used instead.
(5) In smack_file_send_sigiotask(), we need to allow privileged processes to
receive SIGIO on files they're manipulating.
(6) In smack_task_wait(), we let a process wait for a privileged process,
whether or not the process doing the waiting is privileged.
I've tested this with the LTP SELinux and syscalls testscripts.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ae9bec..03fc6a8 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1738,24 +1738,34 @@
/* Hook functions begin here. */
-static int selinux_ptrace(struct task_struct *parent,
- struct task_struct *child,
- unsigned int mode)
+static int selinux_ptrace_may_access(struct task_struct *child,
+ unsigned int mode)
{
int rc;
- rc = secondary_ops->ptrace(parent, child, mode);
+ rc = secondary_ops->ptrace_may_access(child, mode);
if (rc)
return rc;
if (mode == PTRACE_MODE_READ) {
- struct task_security_struct *tsec = parent->security;
+ struct task_security_struct *tsec = current->security;
struct task_security_struct *csec = child->security;
return avc_has_perm(tsec->sid, csec->sid,
SECCLASS_FILE, FILE__READ, NULL);
}
- return task_has_perm(parent, child, PROCESS__PTRACE);
+ return task_has_perm(current, child, PROCESS__PTRACE);
+}
+
+static int selinux_ptrace_traceme(struct task_struct *parent)
+{
+ int rc;
+
+ rc = secondary_ops->ptrace_traceme(parent);
+ if (rc)
+ return rc;
+
+ return task_has_perm(parent, current, PROCESS__PTRACE);
}
static int selinux_capget(struct task_struct *target, kernel_cap_t *effective,
@@ -5346,7 +5356,8 @@
static struct security_operations selinux_ops = {
.name = "selinux",
- .ptrace = selinux_ptrace,
+ .ptrace_may_access = selinux_ptrace_may_access,
+ .ptrace_traceme = selinux_ptrace_traceme,
.capget = selinux_capget,
.capset_check = selinux_capset_check,
.capset_set = selinux_capset_set,