Re: [PATCH v11 11/11] seccomp: implement SECCOMP_FILTER_FLAG_TSYNC
From: David Drysdale <hidden>
Date: 2014-07-17 15:05:23
Also in:
linux-arch, linux-arm-kernel, linux-mips, lkml
On Wed, Jul 16, 2014 at 10:50 PM, Kees Cook [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 9065d2c79c56..2125b83ccfd4 100644 +/** + * seccomp_can_sync_threads: checks if all threads can be synchronized + * + * Expects sighand and cred_guard_mutex locks to be held. + * + * Returns 0 on success, -ve on error, or the pid of a thread which was + * either not in the correct seccomp mode or it did not have an ancestral + * seccomp filter. + */ +static inline pid_t seccomp_can_sync_threads(void) +{ + struct task_struct *thread, *caller; + + BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); + BUG_ON(!spin_is_locked(¤t->sighand->siglock)); + + if (current->seccomp.mode != SECCOMP_MODE_FILTER) + return -EACCES;
Quick question -- is it possible to apply the first filter and also synchronize it across threads in the same operation? If so, does this arm also need to cope with seccomp.mode being SECCOMP_MODE_DISABLED? [seccomp_set_mode_filter() looks to call this via seccomp_attach_filter() before it does seccomp_assign_mode()]
+
+ /* Validate all threads being eligible for synchronization. */
+ caller = current;
+ for_each_thread(caller, thread) {
+ pid_t failed;
+
+ if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
+ (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
+ is_ancestor(thread->seccomp.filter,
+ caller->seccomp.filter)))
+ continue;
+
+ /* Return the first thread that cannot be synchronized. */
+ failed = task_pid_vnr(thread);
+ /* If the pid cannot be resolved, then return -ESRCH */
+ if (unlikely(WARN_ON(failed == 0)))
+ failed = -ESRCH;
+ return failed;
+ }
+
+ return 0;
+}