Fix UB in add-debug libelfin library when calling front() on an empty string

Woazboat · Woazboat · commit 03207d02fd71 · 2023-03-25T23:15:58.000+01:00
Bug found in SWEB by https://github.com/Ferdi265 Open pull request on the upstream project that's been ignored so far... aclements/libelfin#63
diff --git a/utils/add-debug/dwarf/cursor.cc b/utils/add-debug/dwarf/cursor.cc
@@ -86,7 +86,7 @@ cursor::string(std::string &out)
         size_t size;
         const char *p = this->cstr(&size);
         out.resize(size);
-        memmove(&out.front(), p, size);
+        if (size) memmove(&out.front(), p, size);
 }
 
 const char *

Original file line number	Diff line number	Diff line change
`@@ -86,7 +86,7 @@ cursor::string(std::string &out)`
`86`	`86`	`size_t size;`
`87`	`87`	`const char *p = this->cstr(&size);`
`88`	`88`	`out.resize(size);`
`89`		`- memmove(&out.front(), p, size);`
	`89`	`+ if (size) memmove(&out.front(), p, size);`
`90`	`90`	`}`
`91`	`91`
`92`	`92`	`const char *`