setexpr: Correct buffer overflow bug and enable tests

At present when more than one substitution is made this function
overwrites its buffers. Fix this bug and update the tests now that they
can pass.

Also update the debug code to show all substrings, since at present it
omits the final one.

Fixes: 855f18ea ("setexpr: add regex substring matching and substitution")
Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/setexpr.c

@@ -155,11 +155,11 @@ int setexpr_regex_sub(char *data, uint data_size, char *nbuf, uint nbuf_size,
 
 		(void) memset(caps, 0, sizeof(caps));
 
-		res = slre_match(&slre, datap, len, caps);
+		res = slre_match(&slre, datap, len - (datap - data), caps);
 
 		debug("Result: %d\n", res);
 
-		for (i = 0; i < slre.num_caps; i++) {
+		for (i = 0; i <= slre.num_caps; i++) {
 			if (caps[i].len > 0) {
 				debug("Substring %d: [%.*s]\n", i,
 					caps[i].len, caps[i].ptr);
@@ -231,7 +231,7 @@ int setexpr_regex_sub(char *data, uint data_size, char *nbuf, uint nbuf_size,
 					break;
 
 				np = substitute(np, &nlen,
-					nbuf_size,
+					nbuf_size - (np - nbuf),
 					backref, 2,
 					caps[i].ptr, caps[i].len);
 
@@ -241,8 +241,8 @@ int setexpr_regex_sub(char *data, uint data_size, char *nbuf, uint nbuf_size,
 		}
 		debug("## SUBST(2) ## %s\n", nbuf);
 
-		datap = substitute(datap, &len, data_size, old, olen,
-				   nbuf, nlen);
+		datap = substitute(datap, &len, data_size - (datap - data),
+				   old, olen, nbuf, nlen);
 
 		if (datap == NULL)
 			return 1;

test/cmd/setexpr.c

@@ -166,12 +166,10 @@ static int setexpr_test_regex(struct unit_test_state *uts)
 
 	/* Global substitution */
 	ut_assertok(run_command("setenv fred 'this is a test'", 0));
-	if (0) {
-		/* Causes a crash at present due to a bug in setexpr */
-		ut_assertok(run_command("setexpr fred gsub is us", 0));
-		val = env_get("fred");
-		ut_asserteq_str("thus us a test", val);
-	}
+	ut_assertok(run_command("setexpr fred gsub is us", 0));
+	val = env_get("fred");
+	ut_asserteq_str("thus us a test", val);
+
 	/* Global substitution */
 	ut_assertok(run_command("setenv fred 'this is a test'", 0));
 	ut_assertok(run_command("setenv mary 'this is a test'", 0));
@@ -195,14 +193,9 @@ static int setexpr_test_regex_inc(struct unit_test_state *uts)
 	buf = map_sysmem(0, BUF_SIZE);
 
 	ut_assertok(run_command("setenv fred 'this is a test'", 0));
-	if (0) {
-		/* Causes a crash at present due to a bug in setexpr */
-		ut_assertok(run_command("setexpr fred gsub is much_longer_string",
-					0));
-		val = env_get("fred");
-		ut_asserteq_str("thmuch_longer_string much_longer_string a test",
-				val);
-	}
+	ut_assertok(run_command("setexpr fred gsub is much_longer_string", 0));
+	val = env_get("fred");
+	ut_asserteq_str("thmuch_longer_string much_longer_string a test", val);
 	unmap_sysmem(buf);
 
 	return 0;
@@ -234,9 +227,6 @@ static int setexpr_test_sub(struct unit_test_state *uts)
 	ut_assertok(setexpr_regex_sub(buf, BUF_SIZE, nbuf, BUF_SIZE, "is",
 				      "us it is longer", true));
 	ut_asserteq_str("thus it is longer us it is longer a test", buf);
-
-	/* The following checks fail at present due to a bug in setexpr */
-	return 0;
 	for (i = BUF_SIZE; i < 0x1000; i++) {
 		ut_assertf(buf[i] == (char)i,
 			   "buf byte at %x should be %02x, got %02x)\n",