libsandbox: do not abort when the target uses bad pointers

If the target passes a bad pointer to the kernel, then trying to extract
the data via ptrace will also throw an error.  The tracing code should not
abort though as there's no valid address to check, and kernel itself will
return an error for us.  Simply return and move on.

URL: https://bugs.gentoo.org/560396
Reported-by: Jeroen Roovers <jer@gentoo.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

5 files changed, 74 insertions, 1 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0f0c249..3627344 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -76,7 +76,8 @@ check_PROGRAMS = \
 	pipe-fork_static_tst \
 	sb_printf_tst \
 	sigsuspend-zsh_tst \
-	sigsuspend-zsh_static_tst
+	sigsuspend-zsh_static_tst \
+	trace-memory_static_tst
 
 dist_check_SCRIPTS = \
 	$(wildcard $(srcdir)/*-[0-9]*.sh) \
diff --git a/tests/script-13.sh b/tests/script-13.sh
new file mode 100755
index 0000000..24a0e3b
--- /dev/null
+++ b/tests/script-13.sh
@@ -0,0 +1,5 @@
+#!/bin/sh
+# make sure poking remote addresses works even when they're bad/unaligned #560396
+[ "${at_xfail}" = "yes" ] && exit 77 # see script-0
+
+trace-memory_static_tst
diff --git a/tests/script.at b/tests/script.at
index f07a8f1..58a5077 100644
--- a/tests/script.at
+++ b/tests/script.at
@@ -10,3 +10,4 @@ SB_CHECK(9, [wait errpipe... done OK!])
 SB_CHECK(10)
 SB_CHECK(11)
 SB_CHECK(12)
+SB_CHECK(13)
diff --git a/tests/tests.h b/tests/tests.h
index 72c678c..51dc68a 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -1,5 +1,9 @@
 #include "headers.h"
 
+/* Make sure assert() works in tests. */
+#undef NDEBUG
+#include <assert.h>
+
 #define _msg(std, fmt, args...) fprintf(std, "%s:%s():%i: " fmt "\n", __FILE__, __func__, __LINE__, ##args)
 #define _stderr_msg(fmt, args...) _msg(stderr, fmt, ##args)
 #define _stderr_pmsg(fmt, args...) _msg(stderr, fmt ": %s", ##args, strerror(errno))
diff --git a/tests/trace-memory_static_tst.c b/tests/trace-memory_static_tst.c
new file mode 100644
index 0000000..14c6477
--- /dev/null
+++ b/tests/trace-memory_static_tst.c
@@ -0,0 +1,62 @@
+/*
+ * Make sure the process_vm_readv func can work with strings with different
+ * alignments and lengths.
+ *
+ * https://bugs.gentoo.org/560396
+ */
+
+/* We want to make some bad calls. */
+#undef _FORTIFY_SOURCES
+
+#include "tests.h"
+
+/* Make sure the buffer spans multiple pages. */
+#define SIZE 0x1000
+/* Make sure the buffer has plenty of slack space before/after. */
+static char buf[SIZE * 8];
+
+/* The smaller the span, the # of calls goes up: O(N*N*2+N). */
+#define COUNT 0x20
+#define STRIDE (SIZE / COUNT)
+
+/* Some hacks to defeat gcc warnings so we can use bad pointers. */
+volatile uintptr_t offset = 0;
+#define non_const_ptr(ptr) ((void *)((uintptr_t)(ptr) + offset))
+
+#define check_ptr(addr) \
+({ \
+	printf("  open(%p)\n", addr); \
+	ret = open(non_const_ptr(addr), O_RDONLY); \
+	assert(ret == -1 && errno == EFAULT); \
+})
+
+int main(int argc, char *argv[])
+{
+	int ret;
+	char *path = PTR_ALIGN_UP((char *)buf, SIZE);
+	size_t start, end;
+
+	setbuf(stdout, NULL);
+
+	printf("some bad pointers\n");
+	check_ptr(NULL);
+	check_ptr((void *)-1);
+
+	printf("lots of good pointers\n");
+	printf("  buf = %p\n", buf);
+	printf("  path = %p\n", path);
+
+	for (start = 0; start < SIZE * 2 + STRIDE; start += STRIDE) {
+		char *p = path + start;
+		for (end = start + STRIDE; end < SIZE * 2 + STRIDE; end += STRIDE) {
+			size_t len = end - start;
+			printf("  open(%p -> %p [+%#zx])\n", p, p + len, len);
+			memset(p, 'a', len);
+			path[end] = '\0';
+			ret = open(p, O_RDONLY);
+			assert(ret == -1 && (errno == ENOENT || errno == ENAMETOOLONG));
+		}
+	}
+
+	return 0;
+}