all: block negative syscall numbers from the filter

We use negative syscalls numbers to indicate syscalls that aren't
supported by a certain arch/ABI and unfortunately there were cases
where these bogus syscall values were finding their way into the
filter.  This patch corrects this and adds a new test to check for
this in the future.

Reported-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Paul Moore <pmoore@redhat.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/tests/29-sim-pseudo_syscall.c b/tests/29-sim-pseudo_syscall.c
new file mode 100644
index 0000000..d909fd8
--- /dev/null
+++ b/tests/29-sim-pseudo_syscall.c
@@ -0,0 +1,71 @@
+/**
+ * Seccomp Library test program
+ *
+ * Copyright (c) 2015 Red Hat <pmoore@redhat.com>
+ * Author: Paul Moore <pmoore@redhat.com>
+ */
+
+/*
+ * This library is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library; if not, see <http://www.gnu.org/licenses>.
+ */
+
+#include <errno.h>
+#include <unistd.h>
+
+#include <seccomp.h>
+
+#include "util.h"
+
+int main(int argc, char *argv[])
+{
+	int rc;
+	struct util_options opts;
+	scmp_filter_ctx ctx = NULL;
+
+	rc = util_getopt(argc, argv, &opts);
+	if (rc < 0)
+		goto out;
+
+	ctx = seccomp_init(SCMP_ACT_ALLOW);
+	if (ctx == NULL)
+		return ENOMEM;
+
+	/* NOTE: we have to be careful here because some ABIs use syscall
+	 *       offsets which could interfere with our test, x86 is safe */
+	rc = seccomp_arch_remove(ctx, SCMP_ARCH_NATIVE);
+	if (rc < 0)
+		goto out;
+	rc = seccomp_arch_add(ctx, SCMP_ARCH_X86);
+	if (rc < 0)
+		goto out;
+
+	/* SCMP_SYS(sysmips) == 4294957190 (unsigned) */
+	rc = seccomp_rule_add(ctx, SCMP_ACT_KILL, SCMP_SYS(sysmips), 0);
+	if (rc < 0)
+		goto out;
+	rc = seccomp_rule_add_exact(ctx, SCMP_ACT_KILL, SCMP_SYS(sysmips), 0);
+	if (rc == 0)
+		goto out;
+	/* -10001 == 4294957295 (unsigned) */
+	rc = seccomp_rule_add_exact(ctx, SCMP_ACT_KILL, -11001, 0);
+	if (rc == 0)
+		goto out;
+
+	rc = util_filter_output(&opts, ctx);
+	if (rc)
+		goto out;
+
+out:
+	seccomp_release(ctx);
+	return (rc < 0 ? -rc : rc);
+}