Fix corner cases of rt_sigpending syscall decoder

* signal (print_sigset_addr_len_limit): New function, cloned from
print_sigset_addr_len with added minimal length argument.
Treat length less than minimal length or greater than NSIG/8 as invalid.
Do not align length to 4-byte boundary.  Align destination buffer
to 4-byte boundary and initialize it with zeroes so that subsequent
call to sprintsigmask_n will not access uninitialized data.
(print_sigset_addr_len): Turn into a wrapper around
print_sigset_addr_len_limit with current_wordsize
as a minimal length argument.
(SYS_FUNC(rt_sigpending)): Call print_sigset_addr_len_limit
instead of print_sigset_addr_len with 1 as a minimal length argument.
* tests/rt_sigpending.c: New file.
* tests/rt_sigpending.test: New test.
* tests/.gitignore: Add rt_sigpending.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(TESTS): Add rt_sigpending.test.

signal.c

@@ -223,28 +223,29 @@ printsignal(int nr)
 	tprints(signame(nr));
 }
 
-void
-print_sigset_addr_len(struct tcb *tcp, long addr, long len)
+static void
+print_sigset_addr_len_limit(struct tcb *tcp, long addr, long len, long min_len)
 {
-	char mask[NSIG / 8];
-
-	/* Here len is usually equals NSIG / 8 or current_wordsize.
+	/*
+	 * Here len is usually equal to NSIG / 8 or current_wordsize.
 	 * But we code this defensively:
 	 */
-	if (len < 0) {
+	if (len < min_len || len > NSIG / 8) {
 		printaddr(addr);
 		return;
 	}
-	if (len >= NSIG / 8)
-		len = NSIG / 8;
-	else
-		len = (len + 3) & ~3;
-
+	int mask[NSIG / 8 / sizeof(int)] = {};
 	if (umoven_or_printaddr(tcp, addr, len, mask))
 		return;
 	tprints(sprintsigmask_n("", mask, len));
 }
 
+void
+print_sigset_addr_len(struct tcb *tcp, long addr, long len)
+{
+	print_sigset_addr_len_limit(tcp, addr, len, current_wordsize);
+}
+
 SYS_FUNC(sigsetmask)
 {
 	if (entering(tcp)) {
@@ -613,7 +614,8 @@ SYS_FUNC(rt_sigpending)
 		 * This allows non-rt sigpending() syscall
 		 * to reuse rt_sigpending() code in kernel.
 		 */
-		print_sigset_addr_len(tcp, tcp->u_arg[0], tcp->u_arg[1]);
+		print_sigset_addr_len_limit(tcp, tcp->u_arg[0],
+					    tcp->u_arg[1], 1);
 		tprintf(", %lu", tcp->u_arg[1]);
 	}
 	return 0;

tests/.gitignore

@@ -81,6 +81,7 @@ readlinkat
 readv
 recvmsg
 restart_syscall
+rt_sigpending
 rt_sigqueueinfo
 sched_xetaffinity
 sched_xetattr

tests/Makefile.am

@@ -129,6 +129,7 @@ check_PROGRAMS = \
 	readv \
 	recvmsg \
 	restart_syscall \
+	rt_sigpending \
 	rt_sigqueueinfo \
 	sched_xetaffinity \
 	sched_xetattr \
@@ -279,6 +280,7 @@ TESTS = \
 	readlinkat.test \
 	readv.test \
 	recvmsg.test \
+	rt_sigpending.test \
 	rt_sigqueueinfo.test \
 	sched_xetaffinity.test \
 	sched_xetattr.test \

tests/rt_sigpending.c

@@ -0,0 +1,125 @@
+/*
+ * This file is part of rt_sigpending strace test.
+ *
+ * Copyright (c) 2016 Dmitry V. Levin <ldv@altlinux.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "tests.h"
+#include <sys/syscall.h>
+
+#ifdef __NR_rt_sigpending
+
+# include <assert.h>
+# include <signal.h>
+# include <stdio.h>
+# include <string.h>
+# include <unistd.h>
+
+static long
+k_sigpending(void *const set, const unsigned long size)
+{
+	return syscall(__NR_rt_sigpending, set, size);
+}
+
+static void
+iterate(const char *const text, unsigned int size, void *set)
+{
+	for (;;) {
+		if (k_sigpending(set, size))
+			perror_msg_and_fail("rt_sigpending");
+		if (size) {
+#if WORDS_BIGENDIAN
+			if (size < sizeof(long))
+				tprintf("rt_sigpending(%s, %u) = 0\n",
+					"[]", size);
+			else
+#endif
+				tprintf("rt_sigpending(%s, %u) = 0\n",
+					text, size);
+		} else {
+			tprintf("rt_sigpending(%p, %u) = 0\n", set, size);
+			break;
+		}
+		size >>= 1;
+		set += size;
+	}
+}
+
+int
+main(void)
+{
+	tprintf("%s", "");
+
+	const unsigned int big_size = 1024 / 8;
+	void *k_set = tail_alloc(big_size);
+	sigset_t *const libc_set = tail_alloc(sizeof(sigset_t));
+
+	sigemptyset(libc_set);
+	if (sigprocmask(SIG_SETMASK, libc_set, NULL))
+		perror_msg_and_fail("sigprocmask");
+
+	memset(k_set, 0, big_size);
+	unsigned int set_size = big_size;
+	for (; set_size; set_size >>= 1, k_set += set_size) {
+		if (!k_sigpending(k_set, set_size))
+			break;
+		tprintf("rt_sigpending(%p, %u) = -1 EINVAL (%m)\n",
+			k_set, set_size);
+	}
+	if (!set_size)
+		perror_msg_and_fail("rt_sigpending");
+	tprintf("rt_sigpending(%s, %u) = 0\n", "[]", set_size);
+
+	iterate("[]", set_size >> 1, k_set + (set_size >> 1));
+
+	void *const efault = k_set + (set_size >> 1);
+	assert(k_sigpending(efault, set_size) == -1);
+	tprintf("rt_sigpending(%p, %u) = -1 EFAULT (%m)\n",
+		efault, set_size);
+
+	sigaddset(libc_set, SIGHUP);
+	if (sigprocmask(SIG_SETMASK, libc_set, NULL))
+		perror_msg_and_fail("sigprocmask");
+	raise(SIGHUP);
+
+	iterate("[HUP]", set_size, k_set);
+
+	sigaddset(libc_set, SIGINT);
+	if (sigprocmask(SIG_SETMASK, libc_set, NULL))
+		perror_msg_and_fail("sigprocmask");
+	raise(SIGINT);
+
+	iterate("[HUP INT]", set_size, k_set);
+
+	tprintf("+++ exited with 0 +++\n");
+	return 0;
+}
+
+#else
+
+SKIP_MAIN_UNDEFINED("__NR_rt_sigpending")
+
+#endif

tests/rt_sigpending.test

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# Check rt_sigpending syscall decoding.
+
+. "${srcdir=.}/init.sh"
+
+run_prog > /dev/null
+OUT="$LOG.out"
+run_strace -a20 -ert_sigpending $args > "$OUT"
+match_diff "$LOG" "$OUT"
+rm -f "$OUT"