In prepare_namespace(), do_mount() can be used instead of ksys_mount() as the first and third argument are const strings in the kernel, the second and fourth argument are passed through anyway, and the fifth argument is NULL. In do_mount_root(), ksys_mount() is called with the first and third argument being already kernelspace strings, which do not need to be copied over from userspace to kernelspace (again). The second and fourth arguments are passed through to do_mount() anyway. The fifth argument, while already residing in kernelspace, needs to be put into a page of its own. Then, do_mount() can be used instead of ksys_mount(). Once this is done, there are no in-kernel users to ksys_mount() left, which can therefore be removed.
Unified · Split
| @@ -3325,8 +3325,8 @@ struct dentry *mount_subtree(struct vfsmount *m, const char *name) · 3324 unmodified lines | ||
| 3325 | 3325 | } |
| 3326 | 3326 | EXPORT_SYMBOL(mount_subtree); |
| 3327 | 3327 | |
| 3328 | −int ksys_mount(const char __user *dev_name, const char __user *dir_name, | |
| 3329 | − const char __user *type, unsigned long flags, void __user *data) | |
| 3328 | +SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
| 3329 | + char __user *, type, unsigned long, flags, void __user *, data) | |
| 3330 | 3330 | { |
| 3331 | 3331 | int ret; |
| 3332 | 3332 | char *kernel_type; |
| @@ -3359,12 +3359,6 @@ out_type: · 26 unmodified lines | ||
| 3359 | 3359 | return ret; |
| 3360 | 3360 | } |
| 3361 | 3361 | |
| 3362 | −SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, | |
| 3363 | − char __user *, type, unsigned long, flags, void __user *, data) | |
| 3364 | −{ | |
| 3365 | − return ksys_mount(dev_name, dir_name, type, flags, data); | |
| 3366 | −} | |
| 3367 | − | |
| 3368 | 3362 | /* |
| 3369 | 3363 | * Create a kernel mount representation for a new, prepared superblock |
| 3370 | 3364 | * (specified by fs_fd) and attach to an open_tree-like file descriptor. |
| @@ -1231,8 +1231,6 @@ asmlinkage long sys_ni_syscall(void); · 1230 unmodified lines | ||
| 1231 | 1231 | * the ksys_xyzyyz() functions prototyped below. |
| 1232 | 1232 | */ |
| 1233 | 1233 | |
| 1234 | −int ksys_mount(const char __user *dev_name, const char __user *dir_name, | |
| 1235 | − const char __user *type, unsigned long flags, void __user *data); | |
| 1236 | 1234 | int ksys_umount(char __user *name, int flags); |
| 1237 | 1235 | int ksys_dup(unsigned int fildes); |
| 1238 | 1236 | int ksys_chroot(const char __user *filename); |
| @@ -387,12 +387,25 @@ static void __init get_fs_names(char *page) · 386 unmodified lines | ||
| 387 | 387 | *s = '\0'; |
| 388 | 388 | } |
| 389 | 389 | |
| 390 | −static int __init do_mount_root(char *name, char *fs, int flags, void *data) | |
| 390 | +static int __init do_mount_root(const char *name, const char *fs, | |
| 391 | + const int flags, const void *data) | |
| 391 | 392 | { |
| 392 | 393 | struct super_block *s; |
| 393 | − int err = ksys_mount(name, "/root", fs, flags, data); | |
| 394 | − if (err) | |
| 395 | − return err; | |
| 394 | + char *data_page; | |
| 395 | + struct page *p; | |
| 396 | + int ret; | |
| 397 | + | |
| 398 | + /* do_mount() requires a full page as fifth argument */ | |
| 399 | + p = alloc_page(GFP_KERNEL); | |
| 400 | + if (!p) | |
| 401 | + return -ENOMEM; | |
| 402 | + | |
| 403 | + data_page = page_address(p); | |
| 404 | + strncpy(data_page, data, PAGE_SIZE - 1); | |
| 405 | + | |
| 406 | + ret = do_mount(name, "/root", fs, flags, data_page); | |
| 407 | + if (ret) | |
| 408 | + goto out; | |
| 396 | 409 | |
| 397 | 410 | ksys_chdir("/root"); |
| 398 | 411 | s = current->fs->pwd.dentry->d_sb; |
| @@ -402,7 +415,10 @@ static int __init do_mount_root(char *name, char *fs, int flags, void *data) · 3 unmodified lines | ||
| 402 | 415 | s->s_type->name, |
| 403 | 416 | sb_rdonly(s) ? " readonly" : "", |
| 404 | 417 | MAJOR(ROOT_DEV), MINOR(ROOT_DEV)); |
| 405 | − return 0; | |
| 418 | + | |
| 419 | +out: | |
| 420 | + put_page(p); | |
| 421 | + return ret; | |
| 406 | 422 | } |
| 407 | 423 | |
| 408 | 424 | void __init mount_block_root(char *name, int flags) |
| @@ -671,7 +687,7 @@ void __init prepare_namespace(void) · 262 unmodified lines | ||
| 671 | 687 | mount_root(); |
| 672 | 688 | out: |
| 673 | 689 | devtmpfs_mount(); |
| 674 | − ksys_mount(".", "/", NULL, MS_MOVE, NULL); | |
| 690 | + do_mount(".", "/", NULL, MS_MOVE, NULL); | |
| 675 | 691 | ksys_chroot("."); |
| 676 | 692 | } |
| 677 | 693 | |