atoi() is only used to parse numbers from arguments, so there's no
trailing garbage.  As a bonus, we reject negative values which makes no
sense.  INT_MAX is just an upper limit.  way too big.

oks?

diff 5a1af3cffe24ad9d9a983a89b5a57b51a5cc18b3 b30480ea2d6abd9e55cb8ea416d02bb6060dd225
commit - 5a1af3cffe24ad9d9a983a89b5a57b51a5cc18b3
commit + b30480ea2d6abd9e55cb8ea416d02bb6060dd225
blob - 96da0572381e10ed35a0196c6425fc0a5ec4f0c6
blob + 30f164cf922efc833a4fa48cdf1f847f977744ff
--- usr.bin/patch/patch.c
+++ usr.bin/patch/patch.c
@@ -542,6 +542,7 @@ get_some_switches(void)
 		{NULL,			0,			0,	0}
 	};
 	int ch;
+	const char *errstr;
 
 	rejname[0] = '\0';
 	Argc_last = Argc;
@@ -598,7 +599,10 @@ get_some_switches(void)
 			force = true;
 			break;
 		case 'F':
-			maxfuzz = atoi(optarg);
+			maxfuzz = strtonum(optarg, 0, INT_MAX, &errstr);
+			if (errstr != NULL)
+				fatal("fuzz factor is %s: %s\n",
+				    errstr, optarg);
 			break;
 		case 'i':
 			if (++filec == MAXFILEC)
@@ -618,7 +622,10 @@ get_some_switches(void)
 			outname = xstrdup(optarg);
 			break;
 		case 'p':
-			strippath = atoi(optarg);
+			strippath = strtonum(optarg, 0, INT_MAX, &errstr);
+			if (errstr != NULL)
+				fatal("strip count is %s: %s\n",
+				    errstr, optarg);
 			break;
 		case 'r':
 			if (strlcpy(rejname, optarg,
@@ -647,7 +654,10 @@ get_some_switches(void)
 			break;
 #ifdef DEBUGGING
 		case 'x':
-			debug = atoi(optarg);
+			debug = strtonum(optarg, 0, INT_MAX, &errstr);
+			if (errstr != NULL)
+				fatal("debug value is %s: %s\n",
+				    errstr, optarg);
 			break;
 #endif
 		default: