[binutils-gdb] asan: dlltool buffer overflow: embedded NUL in string

[Alan Modra]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=6ef4fa071e2c25b71e81a91646b43378cf957388

commit 6ef4fa071e2c25b71e81a91646b43378cf957388
Author: Alan Modra <amodra@gmail.com>
Date:   Wed Nov 3 16:21:42 2021 +1030

    asan: dlltool buffer overflow: embedded NUL in string
    
    yyleng gives the pattern length, xstrdup just copies up to the NUL.
    So it is quite possible writing at an index of yyleng-2 overflows
    the xstrdup allocated string buffer.  xmemdup quite handily avoids
    this problem, even writing the terminating NUL over the trailing
    quote.  Use it in ldlex.l too where we'd already had a report of this
    problem and fixed it by hand, and to implement xmemdup0 in gas.
    
    binutils/
            * deflex.l (single and double quote strings): Use xmemdup.
    gas/
            * as.h (xmemdup0): Use xmemdup.
    ld/
            PR 20906
            * ldlex.l (double quote string): Use xmemdup.

Diff:
---
 binutils/deflex.l |  6 ++----
 gas/as.h          |  4 +---
 ld/ldlex.l        | 16 ++++------------
 3 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/binutils/deflex.l b/binutils/deflex.l
index 1f3ba6532d4..def908c1139 100644
--- a/binutils/deflex.l
+++ b/binutils/deflex.l
@@ -69,14 +69,12 @@ int linenumber;
 		}
 
 "\""[^\"]*"\"" {
-		yylval.id = xstrdup (yytext+1);
-		yylval.id[yyleng-2] = 0;
+		yylval.id = xmemdup (yytext + 1, yyleng - 2, yyleng - 1);
 		return ID;
 		}
 
 "\'"[^\']*"\'" {
-		yylval.id = xstrdup (yytext+1);
-		yylval.id[yyleng-2] = 0;
+		yylval.id = xmemdup (yytext + 1, yyleng - 2, yyleng - 1);
 		return ID;
 		}
 "*".* 		{ }
diff --git a/gas/as.h b/gas/as.h
index 14a768f8889..f3f12fbd2f8 100644
--- a/gas/as.h
+++ b/gas/as.h
@@ -484,9 +484,7 @@ void add_debug_prefix_map (const char *);
 static inline char *
 xmemdup0 (const char *in, size_t len)
 {
-  char *out = (char *) xmalloc (len + 1);
-  out[len] = 0;
-  return (char *) memcpy (out, in, len);
+  return xmemdup (in, len, len + 1);
 }
 
 struct expressionS;
diff --git a/ld/ldlex.l b/ld/ldlex.l
index 6aeba6de656..5db1e731b74 100644
--- a/ld/ldlex.l
+++ b/ld/ldlex.l
@@ -431,18 +431,10 @@ V_IDENTIFIER [*?.$_a-zA-Z\[\]\-\!\^\\]([*?.$_a-zA-Z0-9\[\]\-\!\^\\]|::)*
 	}
 
 <SCRIPT,EXPRESSION,WILD,VERS_NODE,INPUTLIST>"\""[^\"]*"\"" {
-					/* No matter the state, quotes
-					   give what's inside.  */
-					bfd_size_type len;
-					yylval.name = xstrdup (yytext + 1);
-					/* PR ld/20906.  A corrupt input file
-					   can contain bogus strings.  */
-					len = strlen (yylval.name);
-					if (len > (bfd_size_type) yyleng - 2)
-					  len = yyleng - 2;
-					yylval.name[len] = 0;
-					return NAME;
-				}
+		/* No matter the state, quotes give what's inside.  */
+		yylval.name = xmemdup (yytext + 1, yyleng - 2, yyleng - 1);
+		return NAME;
+	}
 
 <SCRIPT,EXPRESSION,WILD,VERS_START,VERS_NODE,VERS_SCRIPT,INPUTLIST>"\n" {
 				lineno++; }