diff --git a/include/utils/Unicode.h b/include/utils/Unicode.h
index a006082..a13f347 100644
--- a/include/utils/Unicode.h
+++ b/include/utils/Unicode.h
@@ -31,7 +31,7 @@
 char16_t *strncpy16(char16_t *, const char16_t *, size_t);
 char16_t *strstr16(const char16_t*, const char16_t*);
 
-// Version of comparison that supports embedded nulls.
+// Version of comparison that supports embedded NULs.
 // This is different than strncmp() because we don't stop
 // at a nul character and consider the strings to be different
 // if the lengths are different (thus we need to supply the
@@ -58,7 +58,7 @@
  * large enough to store the string, the part of the "src" string is stored
  * into "dst" as much as possible. See the examples for more detail.
  * Returns the size actually used for storing the string.
- * dst" is not null-terminated when dst_len is fully used (like strncpy).
+ * dst" is not nul-terminated when dst_len is fully used (like strncpy).
  *
  * Example 1
  * "src" == \u3042\u3044 (\xE3\x81\x82\xE3\x81\x84)
@@ -67,7 +67,7 @@
  * ->
  * Returned value == 6
  * "dst" becomes \xE3\x81\x82\xE3\x81\x84\0
- * (note that "dst" is null-terminated)
+ * (note that "dst" is nul-terminated)
  *
  * Example 2
  * "src" == \u3042\u3044 (\xE3\x81\x82\xE3\x81\x84)
@@ -76,7 +76,7 @@
  * ->
  * Returned value == 3
  * "dst" becomes \xE3\x81\x82\0
- * (note that "dst" is null-terminated, but \u3044 is not stored in "dst"
+ * (note that "dst" is nul-terminated, but \u3044 is not stored in "dst"
  * since "dst" does not have enough size to store the character)
  *
  * Example 3
@@ -86,9 +86,9 @@
  * ->
  * Returned value == 6
  * "dst" becomes \xE3\x81\x82\xE3\x81\x84
- * (note that "dst" is NOT null-terminated, like strncpy)
+ * (note that "dst" is NOT nul-terminated, like strncpy)
  */
-void utf32_to_utf8(const char32_t* src, size_t src_len, char* dst);
+void utf32_to_utf8(const char32_t* src, size_t src_len, char* dst, size_t dst_len);
 
 /**
  * Returns the unicode value at "index".
@@ -108,9 +108,9 @@
 /**
  * Converts a UTF-16 string to UTF-8. The destination buffer must be large
  * enough to fit the UTF-16 as measured by utf16_to_utf8_length with an added
- * NULL terminator.
+ * NUL terminator.
  */
-void utf16_to_utf8(const char16_t* src, size_t src_len, char* dst);
+void utf16_to_utf8(const char16_t* src, size_t src_len, char* dst, size_t dst_len);
 
 /**
  * Returns the length of "src" when "src" is valid UTF-8 string.
@@ -118,7 +118,7 @@
  * is an invalid string.
  *
  * This function should be used to determine whether "src" is valid UTF-8
- * characters with valid unicode codepoints. "src" must be null-terminated.
+ * characters with valid unicode codepoints. "src" must be nul-terminated.
  *
  * If you are going to use other utf8_to_... functions defined in this header
  * with string which may not be valid UTF-8 with valid codepoint (form 0 to
@@ -138,35 +138,38 @@
 /**
  * Stores a UTF-32 string converted from "src" in "dst". "dst" must be large
  * enough to store the entire converted string as measured by
- * utf8_to_utf32_length plus space for a NULL terminator.
+ * utf8_to_utf32_length plus space for a NUL terminator.
  */
 void utf8_to_utf32(const char* src, size_t src_len, char32_t* dst);
 
 /**
- * Returns the UTF-16 length of UTF-8 string "src".
+ * Returns the UTF-16 length of UTF-8 string "src". Returns -1 in case
+ * it's invalid utf8. No buffer over-read occurs because of bound checks. Using overreadIsFatal you
+ * can ask to log a message and fail in case the invalid utf8 could have caused an override if no
+ * bound checks were used (otherwise -1 is returned).
  */
-ssize_t utf8_to_utf16_length(const uint8_t* src, size_t srcLen);
+ssize_t utf8_to_utf16_length(const uint8_t* src, size_t srcLen, bool overreadIsFatal = false);
 
 /**
  * Convert UTF-8 to UTF-16 including surrogate pairs.
- * Returns a pointer to the end of the string (where a null terminator might go
- * if you wanted to add one).
+ * Returns a pointer to the end of the string (where a NUL terminator might go
+ * if you wanted to add one). At most dstLen characters are written; it won't emit half a surrogate
+ * pair. If dstLen == 0 nothing is written and dst is returned. If dstLen > SSIZE_MAX it aborts
+ * (this being probably a negative number returned as an error and casted to unsigned).
  */
-char16_t* utf8_to_utf16_no_null_terminator(const uint8_t* src, size_t srcLen, char16_t* dst);
+char16_t* utf8_to_utf16_no_null_terminator(
+        const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
 
 /**
- * Convert UTF-8 to UTF-16 including surrogate pairs. The destination buffer
- * must be large enough to hold the result as measured by utf8_to_utf16_length
- * plus an added NULL terminator.
+ * Convert UTF-8 to UTF-16 including surrogate pairs. At most dstLen - 1
+ * characters are written; it won't emit half a surrogate pair; and a NUL terminator is appended
+ * after. dstLen - 1 can be measured beforehand using utf8_to_utf16_length. Aborts if dstLen == 0
+ * (at least one character is needed for the NUL terminator) or dstLen > SSIZE_MAX (the latter
+ * case being likely a negative number returned as an error and casted to unsigned) . Returns a
+ * pointer to the NUL terminator.
  */
-void utf8_to_utf16(const uint8_t* src, size_t srcLen, char16_t* dst);
-
-/**
- * Like utf8_to_utf16_no_null_terminator, but you can supply a maximum length of the
- * decoded string.  The decoded string will fill up to that length; if it is longer
- * the returned pointer will be to the character after dstLen.
- */
-char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
+char16_t *utf8_to_utf16(
+        const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
 
 }
 
diff --git a/libutils/String16.cpp b/libutils/String16.cpp
index ac12d8a..9f5cfea 100644
--- a/libutils/String16.cpp
+++ b/libutils/String16.cpp
@@ -71,7 +71,7 @@
         u8cur = (const uint8_t*) u8str;
         char16_t* u16str = (char16_t*)buf->data();
 
-        utf8_to_utf16(u8cur, u8len, u16str);
+        utf8_to_utf16(u8cur, u8len, u16str, ((size_t) u16len) + 1);
 
         //printf("Created UTF-16 string from UTF-8 \"%s\":", in);
         //printHexData(1, str, buf->size(), 16, 1);
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index ad45282..cacaf91 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -104,20 +104,21 @@
 {
     if (len == 0) return getEmptyString();
 
-    const ssize_t bytes = utf16_to_utf8_length(in, len);
-    if (bytes < 0) {
+     // Allow for closing '\0'
+    const ssize_t resultStrLen = utf16_to_utf8_length(in, len) + 1;
+    if (resultStrLen < 1) {
         return getEmptyString();
     }
 
-    SharedBuffer* buf = SharedBuffer::alloc(bytes+1);
+    SharedBuffer* buf = SharedBuffer::alloc(resultStrLen);
     ALOG_ASSERT(buf, "Unable to allocate shared buffer");
     if (!buf) {
         return getEmptyString();
     }
 
-    char* str = (char*)buf->data();
-    utf16_to_utf8(in, len, str);
-    return str;
+    char* resultStr = (char*)buf->data();
+    utf16_to_utf8(in, len, resultStr, resultStrLen);
+    return resultStr;
 }
 
 static char* allocFromUTF32(const char32_t* in, size_t len)
@@ -126,21 +127,21 @@
         return getEmptyString();
     }
 
-    const ssize_t bytes = utf32_to_utf8_length(in, len);
-    if (bytes < 0) {
+    const ssize_t resultStrLen = utf32_to_utf8_length(in, len) + 1;
+    if (resultStrLen < 1) {
         return getEmptyString();
     }
 
-    SharedBuffer* buf = SharedBuffer::alloc(bytes+1);
+    SharedBuffer* buf = SharedBuffer::alloc(resultStrLen);
     ALOG_ASSERT(buf, "Unable to allocate shared buffer");
     if (!buf) {
         return getEmptyString();
     }
 
-    char* str = (char*) buf->data();
-    utf32_to_utf8(in, len, str);
+    char* resultStr = (char*) buf->data();
+    utf32_to_utf8(in, len, resultStr, resultStrLen);
 
-    return str;
+    return resultStr;
 }
 
 // ---------------------------------------------------------------------------
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index f1f8bc9..5f96efa 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -14,8 +14,10 @@
  * limitations under the License.
  */
 
+#include <log/log.h>
 #include <utils/Unicode.h>
 
+#include <limits.h>
 #include <stddef.h>
 
 #if defined(_WIN32)
@@ -182,7 +184,7 @@
     return ret;
 }
 
-void utf32_to_utf8(const char32_t* src, size_t src_len, char* dst)
+void utf32_to_utf8(const char32_t* src, size_t src_len, char* dst, size_t dst_len)
 {
     if (src == NULL || src_len == 0 || dst == NULL) {
         return;
@@ -193,9 +195,12 @@
     char *cur = dst;
     while (cur_utf32 < end_utf32) {
         size_t len = utf32_codepoint_utf8_length(*cur_utf32);
+        LOG_ALWAYS_FATAL_IF(dst_len < len, "%zu < %zu", dst_len, len);
         utf32_codepoint_to_utf8((uint8_t *)cur, *cur_utf32++, len);
         cur += len;
+        dst_len -= len;
     }
+    LOG_ALWAYS_FATAL_IF(dst_len < 1, "dst_len < 1: %zu < 1", dst_len);
     *cur = '\0';
 }
 
@@ -348,7 +353,7 @@
            : 0);
 }
 
-void utf16_to_utf8(const char16_t* src, size_t src_len, char* dst)
+void utf16_to_utf8(const char16_t* src, size_t src_len, char* dst, size_t dst_len)
 {
     if (src == NULL || src_len == 0 || dst == NULL) {
         return;
@@ -369,9 +374,12 @@
             utf32 = (char32_t) *cur_utf16++;
         }
         const size_t len = utf32_codepoint_utf8_length(utf32);
+        LOG_ALWAYS_FATAL_IF(dst_len < len, "%zu < %zu", dst_len, len);
         utf32_codepoint_to_utf8((uint8_t*)cur, utf32, len);
         cur += len;
+        dst_len -= len;
     }
+    LOG_ALWAYS_FATAL_IF(dst_len < 1, "%zu < 1", dst_len);
     *cur = '\0';
 }
 
@@ -432,10 +440,10 @@
     const char16_t* const end = src + src_len;
     while (src < end) {
         if ((*src & 0xFC00) == 0xD800 && (src + 1) < end
-                && (*++src & 0xFC00) == 0xDC00) {
+                && (*(src + 1) & 0xFC00) == 0xDC00) {
             // surrogate pairs are always 4 bytes.
             ret += 4;
-            src++;
+            src += 2;
         } else {
             ret += utf32_codepoint_utf8_length((char32_t) *src++);
         }
@@ -535,7 +543,7 @@
     //printf("Char at %p: len=%d, utf-16=%p\n", src, length, (void*)result);
 }
 
-ssize_t utf8_to_utf16_length(const uint8_t* u8str, size_t u8len)
+ssize_t utf8_to_utf16_length(const uint8_t* u8str, size_t u8len, bool overreadIsFatal)
 {
     const uint8_t* const u8end = u8str + u8len;
     const uint8_t* u8cur = u8str;
@@ -545,6 +553,20 @@
     while (u8cur < u8end) {
         u16measuredLen++;
         int u8charLen = utf8_codepoint_len(*u8cur);
+        // Malformed utf8, some characters are beyond the end.
+        // Cases:
+        // If u8charLen == 1, this becomes u8cur >= u8end, which cannot happen as u8cur < u8end,
+        // then this condition fail and we continue, as expected.
+        // If u8charLen == 2, this becomes u8cur + 1 >= u8end, which fails only if
+        // u8cur == u8end - 1, that is, there was only one remaining character to read but we need
+        // 2 of them. This condition holds and we return -1, as expected.
+        if (u8cur + u8charLen - 1 >= u8end) {
+            if (overreadIsFatal) {
+                LOG_ALWAYS_FATAL("Attempt to overread computing length of utf8 string");
+            } else {
+                return -1;
+            }
+        }
         uint32_t codepoint = utf8_to_utf32_codepoint(u8cur, u8charLen);
         if (codepoint > 0xFFFF) u16measuredLen++; // this will be a surrogate pair in utf16
         u8cur += u8charLen;
@@ -561,38 +583,21 @@
     return u16measuredLen;
 }
 
-char16_t* utf8_to_utf16_no_null_terminator(const uint8_t* u8str, size_t u8len, char16_t* u16str)
-{
-    const uint8_t* const u8end = u8str + u8len;
-    const uint8_t* u8cur = u8str;
-    char16_t* u16cur = u16str;
-
-    while (u8cur < u8end) {
-        size_t u8len = utf8_codepoint_len(*u8cur);
-        uint32_t codepoint = utf8_to_utf32_codepoint(u8cur, u8len);
-
-        // Convert the UTF32 codepoint to one or more UTF16 codepoints
-        if (codepoint <= 0xFFFF) {
-            // Single UTF16 character
-            *u16cur++ = (char16_t) codepoint;
-        } else {
-            // Multiple UTF16 characters with surrogates
-            codepoint = codepoint - 0x10000;
-            *u16cur++ = (char16_t) ((codepoint >> 10) + 0xD800);
-            *u16cur++ = (char16_t) ((codepoint & 0x3FF) + 0xDC00);
-        }
-
-        u8cur += u8len;
-    }
-    return u16cur;
-}
-
-void utf8_to_utf16(const uint8_t* u8str, size_t u8len, char16_t* u16str) {
-    char16_t* end = utf8_to_utf16_no_null_terminator(u8str, u8len, u16str);
+char16_t* utf8_to_utf16(const uint8_t* u8str, size_t u8len, char16_t* u16str, size_t u16len) {
+    // A value > SSIZE_MAX is probably a negative value returned as an error and casted.
+    LOG_ALWAYS_FATAL_IF(u16len == 0 || u16len > SSIZE_MAX, "u16len is %zu", u16len);
+    char16_t* end = utf8_to_utf16_no_null_terminator(u8str, u8len, u16str, u16len - 1);
     *end = 0;
+    return end;
 }
 
-char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
+char16_t* utf8_to_utf16_no_null_terminator(
+        const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
+    if (dstLen == 0) {
+        return dst;
+    }
+    // A value > SSIZE_MAX is probably a negative value returned as an error and casted.
+    LOG_ALWAYS_FATAL_IF(dstLen > SSIZE_MAX, "dstLen is %zu", dstLen);
     const uint8_t* const u8end = src + srcLen;
     const uint8_t* u8cur = src;
     const char16_t* const u16end = dst + dstLen;
diff --git a/libutils/tests/String8_test.cpp b/libutils/tests/String8_test.cpp
index 01e64f6..3947a5f 100644
--- a/libutils/tests/String8_test.cpp
+++ b/libutils/tests/String8_test.cpp
@@ -17,6 +17,7 @@
 #define LOG_TAG "String8_test"
 #include <utils/Log.h>
 #include <utils/String8.h>
+#include <utils/String16.h>
 
 #include <gtest/gtest.h>
 
@@ -77,4 +78,22 @@
     EXPECT_EQ(NO_MEMORY, String8("").setTo(in, SIZE_MAX));
 }
 
+// http://b/29250543
+TEST_F(String8Test, CorrectInvalidSurrogate) {
+    // d841d8 is an invalid start for a surrogate pair. Make sure this is handled by ignoring the
+    // first character in the pair and handling the rest correctly.
+    String16 string16(u"\xd841\xd841\xdc41\x0000");
+    String8 string8(string16);
+
+    EXPECT_EQ(4U, string8.length());
+}
+
+TEST_F(String8Test, CheckUtf32Conversion) {
+    // Since bound checks were added, check the conversion can be done without fatal errors.
+    // The utf8 lengths of these are chars are 1 + 2 + 3 + 4 = 10.
+    const char32_t string32[] = U"\x0000007f\x000007ff\x0000911\x0010fffe";
+    String8 string8(string32);
+    EXPECT_EQ(10U, string8.length());
+}
+
 }
diff --git a/libutils/tests/Unicode_test.cpp b/libutils/tests/Unicode_test.cpp
index c263f75..d23e43a 100644
--- a/libutils/tests/Unicode_test.cpp
+++ b/libutils/tests/Unicode_test.cpp
@@ -98,7 +98,7 @@
 
     char16_t output[1 + 1 + 1 + 2 + 1]; // Room for NULL
 
-    utf8_to_utf16(str, sizeof(str), output);
+    utf8_to_utf16(str, sizeof(str), output, sizeof(output) / sizeof(output[0]));
 
     EXPECT_EQ(0x0030, output[0])
             << "should be U+0030";
@@ -147,4 +147,15 @@
     EXPECT_EQ(nullptr, result);
 }
 
+// http://b/29267949
+// Test that overreading in utf8_to_utf16_length is detected
+TEST_F(UnicodeTest, InvalidUtf8OverreadDetected) {
+    // An utf8 char starting with \xc4 is two bytes long.
+    // Add extra zeros so no extra memory is read in case the code doesn't
+    // work as expected.
+    static char utf8[] = "\xc4\x00\x00\x00";
+    ASSERT_DEATH(utf8_to_utf16_length((uint8_t *) utf8, strlen(utf8),
+            true /* overreadIsFatal */), "" /* regex for ASSERT_DEATH */);
+}
+
 }