kboot: Fix an off by one error

[imp]

Summary

Fix an off-by-one error that would mean we'd get stuck on the newline if
ACPI= wasn't first.

Sponsored by: Netflix

stand/kboot/main.c

default:
                 /*
                  * Ignore unknown operations, just like Linux kernel built
                  * without CONFIG_SECCOMP.
                  */
                 return (EINVAL);
         }
 }
 
-#ifndef COMPAT_LINUX32
+/*
+ * Custom version of exec_copyin_args(), to copy out argument and environment
+ * strings from the old process address space into the temporary string buffer.
+ * Based on freebsd32_exec_copyin_args.
+ */
+static int
+linux_exec_copyin_args(struct image_args *args, const char *fname,
+    enum uio_seg segflg, l_uintptr_t *argv, l_uintptr_t *envv)
+{
+        char *argp, *envp;
+        l_uintptr_t *ptr, arg;
+        int error;
+
+        bzero(args, sizeof(*args));
+        if (argv == NULL)
+                return (EFAULT);
+
+        /*
+         * Allocate demand-paged memory for the file name, argument, and
+         * environment strings.
+         */
+        error = exec_alloc_args(args);
+        if (error != 0)
+                return (error);
+
+        /*
+         * Copy the file name.
+         */
+        error = exec_args_add_fname(args, fname, segflg);
+        if (error != 0)
+                goto err_exit;
+
+        /*
+         * extract arguments first
+         */
+        ptr = argv;
+        for (;;) {
+                error = copyin(ptr++, &arg, sizeof(arg));
+                if (error)
+                        goto err_exit;
+                if (arg == 0)
+                        break;
+                argp = PTRIN(arg);
+                error = exec_args_add_arg(args, argp, UIO_USERSPACE);
+                if (error != 0)
+                        goto err_exit;
+        }
+
+        /*
+         * This comment is from Linux do_execveat_common:
+         * When argv is empty, add an empty string ("") as argv[0] to
+         * ensure confused userspace programs that start processing
+         * from argv[1] won't end up walking envp.
+         */
+        if (args->argc == 0 &&
+            (error = exec_args_add_arg(args, "", UIO_SYSSPACE) != 0))
+                goto err_exit;
+
+        /*
+         * extract environment strings
+         */
+        if (envv) {
+                ptr = envv;
+                for (;;) {
+                        error = copyin(ptr++, &arg, sizeof(arg));
+                        if (error)
+                                goto err_exit;
+                        if (arg == 0)
+                                break;
+                        envp = PTRIN(arg);
+                        error = exec_args_add_env(args, envp, UIO_USERSPACE);
+                        if (error != 0)
+                                goto err_exit;
+                }
+        }
+
+        return (0);
+
+err_exit:
+        exec_free_args(args);
+        return (error);
+}
+
 int
 linux_execve(struct thread *td, struct linux_execve_args *args)
 {
         struct image_args eargs;
         int error;
 
         LINUX_CTR(execve);
 
-        error = exec_copyin_args(&eargs, args->path, UIO_USERSPACE,
+        error = linux_exec_copyin_args(&eargs, args->path, UIO_USERSPACE,
             args->argp, args->envp);
         if (error == 0)
                 error = linux_common_execve(td, &eargs);
         AUDIT_SYSCALL_EXIT(error == EJUSTRETURN ? 0 : error, td);
         return (error);
 }
-#endif