uuidgen: generate UUIDs in bounded batches to respect kernel limit

The kernel uuidgen(2) system call enforces a hard limit of 2048 UUIDs per
call, but uuidgen(1) attempted to generate arbitrarily many UUIDs in a
single invocation and allocate memory proportional to the request size.

Generate UUIDs in fixed-size batches instead to:
- respect the kernel ABI
- avoid unbounded memory allocation
- prevent integer overflow in size calculations
- preserve streaming behavior for large -n values

Signed-off-by: NVSRahul <[email protected]>

Author: NVSRahul

bin/uuidgen/uuidgen.c

@@ -34,6 +34,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <uuid.h>
+#define UUID_BATCH_SIZE 2048
 
 static void
 usage(void)
@@ -156,46 +157,51 @@ main(int argc, char *argv[])
 	if (count == -1)
 		count = 1;
 
-	store = (uuid_t *)malloc(sizeof(uuid_t) * count);
-	if (store == NULL)
-		err(1, "malloc()");
-
-	if (!iterate) {
-		/* Get them all in a single batch */
-		if (version == 1) {
-			if (uuidgen(store, count) != 0)
-				err(1, "uuidgen()");
-		} else if (version == 4) {
-			if (uuidgen_v4(store, count) != 0)
-				err(1, "uuidgen_v4()");
-		} else {
-			err(1, "unsupported version");
-		}
-	} else {
-		uuid = store;
-		for (i = 0; i < count; i++) {
-			if (version == 1) {
-				if (uuidgen(uuid++, 1) != 0)
-					err(1, "uuidgen()");
-			} else if (version == 4) {
-				if (uuidgen_v4(uuid++, 1) != 0)
-					err(1, "uuidgen_v4()");
-			} else {
-				err(1, "unsupported version");
-			}
-		}
-	}
-
-	uuid = store;
-	while (count--) {
-		tostring(uuid++, &p, &status);
-		if (status != uuid_s_ok)
-			err(1, "cannot stringify a UUID");
-		fprintf(fp, "%s\n", p);
-		free(p);
-	}
+    store = calloc(UUID_BATCH_SIZE, sizeof(uuid_t));
+    if (store == NULL)
+        err(1, "calloc()");
+
+    while (count > 0) {
+        int batch = (count > UUID_BATCH_SIZE) ? UUID_BATCH_SIZE : count;
+
+        if (!iterate) {
+            if (version == 1) {
+                if (uuidgen(store, batch) != 0)
+                    err(1, "uuidgen()");
+            } else if (version == 4) {
+                if (uuidgen_v4(store, batch) != 0)
+                    err(1, "uuidgen_v4()");
+            } else {
+                err(1, "unsupported version");
+            }
+        } else {
+            uuid = store;
+            for (i = 0; i < batch; i++) {
+                if (version == 1) {
+                    if (uuidgen(uuid++, 1) != 0)
+                        err(1, "uuidgen()");
+                } else if (version == 4) {
+                    if (uuidgen_v4(uuid++, 1) != 0)
+                        err(1, "uuidgen_v4()");
+                } else {
+                    err(1, "unsupported version");
+                }
+            }
+        }
+
+        uuid = store;
+        for (i = 0; i < batch; i++) {
+            tostring(uuid++, &p, &status);
+            if (status != uuid_s_ok)
+                err(1, "cannot stringify a UUID");
+            fprintf(fp, "%s\n", p);
+            free(p);
+        }
+
+        count -= batch;
+    }
+    free(store);
 
-	free(store);
 	if (fp != stdout)
 		fclose(fp);
 	return (0);