libutils: check vsnprintf error
For encoding errors, this function will return a negative value which
causes problems down the line. Check for an error and return. Also,
integer overflows are guarded.
Bug: 161894517
Test: fuzzer test case
Change-Id: Ia85067d4258bde4b875c832d6223db5dd26b8838
Merged-In: Ia85067d4258bde4b875c832d6223db5dd26b8838
(cherry picked from commit ee22384c54d42149491c8b9dbcda0d8c5e88eddc)
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 0025c56..81ec598 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -322,8 +322,14 @@
n = vsnprintf(nullptr, 0, fmt, tmp_args);
va_end(tmp_args);
- if (n != 0) {
+ if (n < 0) return UNKNOWN_ERROR;
+
+ if (n > 0) {
size_t oldLength = length();
+ if ((size_t)n > SIZE_MAX - 1 ||
+ oldLength > SIZE_MAX - (size_t)n - 1) {
+ return NO_MEMORY;
+ }
char* buf = lockBuffer(oldLength + n);
if (buf) {
vsnprintf(buf + oldLength, n + 1, fmt, args);