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Fix potential out of range in String::concat #10942

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Fix potential out of range in String::concat #10942

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3470796
Fix potential out of range in String::concat
TD-er Feb 6, 2025
998ce4c
Allow String::concat(const String &s) with s.buffer() == nullptr
TD-er Feb 6, 2025
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16 changes: 7 additions & 9 deletions cores/esp32/WString.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -311,23 +311,21 @@ bool String::concat(const String &s) {
// Special case if we're concatting ourself (s += s;) since we may end up
// realloc'ing the buffer and moving s.buffer in the method called
if (&s == this) {
unsigned int newlen = 2 * len();
if (!s.buffer()) {
return false;
}
if (s.len() == 0) {
return true;
}
if (!s.buffer()) {
return false;
}
unsigned int newlen = 2 * len();
if (!reserve(newlen)) {
return false;
}
memmove(wbuffer() + len(), buffer(), len());
setLen(newlen);
wbuffer()[len()] = 0;
return true;
} else {
return concat(s.buffer(), s.len());
}
return concat(s.buffer(), s.len());
}

bool String::concat(const char *cstr, unsigned int length) {
Expand All @@ -343,10 +341,10 @@ bool String::concat(const char *cstr, unsigned int length) {
}
if (cstr >= wbuffer() && cstr < wbuffer() + len()) {
// compatible with SSO in ram #6155 (case "x += x.c_str()")
memmove(wbuffer() + len(), cstr, length + 1);
memmove(wbuffer() + len(), cstr, length);
} else {
// compatible with source in flash #6367
memcpy_P(wbuffer() + len(), cstr, length + 1);
memcpy_P(wbuffer() + len(), cstr, length);
}
setLen(newlen);
return true;
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