svn commit: r365055 - head/lib/libc/tests/resolv

[John Baldwin]

Author: jhb
Date: Tue Sep  1 16:20:42 2020
New Revision: 365055
URL: https://svnweb.freebsd.org/changeset/base/365055

Log:
  Fix a buffer overrun.
  
  getln() returns 'len' valid characters.  line[len] is out of bounds.
  
  Reported by:	CHERI
  Reviewed by:	brooks
  Obtained from:	CheriBSD
  MFC after:	2 weeks
  Sponsored by:	DARPA
  Differential Revision:	https://reviews.freebsd.org/D26197

Modified:
  head/lib/libc/tests/resolv/resolv_test.c

Modified: head/lib/libc/tests/resolv/resolv_test.c
==============================================================================
--- head/lib/libc/tests/resolv/resolv_test.c	Tue Sep  1 16:17:21 2020	(r365054)
+++ head/lib/libc/tests/resolv/resolv_test.c	Tue Sep  1 16:20:42 2020	(r365055)
@@ -76,15 +76,15 @@ load(const char *fname)
 	if ((fp = fopen(fname, "r")) == NULL)
 	ATF_REQUIRE(fp != NULL);
 	while ((line = fgetln(fp, &len)) != NULL) {
-		char c = line[len];
+		char c = line[len - 1];
 		char *ptr;
-		line[len] = '\0';
+		line[len - 1] = '\0';
 		for (ptr = strtok(line, WS); ptr; ptr = strtok(NULL, WS)) {
 			if (ptr == '\0' || ptr[0] == '#')
 				continue;
 			sl_add(hosts, strdup(ptr));
 		}
-		line[len] = c;
+		line[len - 1] = c;
 	}
 
 	(void)fclose(fp);