FORTIFY_SOURCE: fortify strrchr

This change compliments 049e58369c37fdeacd0380a6bf1e078d9baf819f

Change-Id: I27d015d70a520713c7472558a3c427f546d36ee4

2 files changed, 30 insertions, 2 deletions

diff --git a/libc/include/string.h b/libc/include/string.h
index 32b9310..2ed74e8 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -240,6 +240,22 @@ char* strchr(const char *s, int c) {
     return __strchr_chk(s, c, bos);
 }
 
+__purefunc extern char* __strrchr_real(const char *, int)
+    __asm__(__USER_LABEL_PREFIX__ "strrchr");
+extern char* __strrchr_chk(const char *, int, size_t);
+
+__BIONIC_FORTIFY_INLINE
+char* strrchr(const char *s, int c) {
+    size_t bos = __builtin_object_size(s, 0);
+
+    // Compiler doesn't know destination size. Don't call __strrchr_chk
+    if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
+        return __strrchr_real(s, c);
+    }
+
+    return __strrchr_chk(s, c, bos);
+}
+
 
 #endif /* defined(__BIONIC_FORTIFY_INLINE) */
 
diff --git a/libc/string/strrchr.c b/libc/string/strrchr.c
index 10c07e6..fc3dc4e 100644
--- a/libc/string/strrchr.c
+++ b/libc/string/strrchr.c
@@ -29,13 +29,19 @@
  */
 
 #include <string.h>
+#include <private/logd.h>
 
 char *
-strrchr(const char *p, int ch)
+__strrchr_chk(const char *p, int ch, size_t s_len)
 {
 	char *save;
 
-	for (save = NULL;; ++p) {
+	for (save = NULL;; ++p, s_len--) {
+		if (s_len == 0) {
+			__libc_android_log_print(ANDROID_LOG_FATAL, "libc",
+				"*** FORTIFY_SOURCE strrchr read beyond buffer ***\n");
+			abort();
+		}
 		if (*p == (char) ch)
 			save = (char *)p;
 		if (!*p)
@@ -43,3 +49,9 @@ strrchr(const char *p, int ch)
 	}
 	/* NOTREACHED */
 }
+
+char *
+strrchr(const char *p, int ch)
+{
+	return __strrchr_chk(p, ch, (size_t) -1);
+}