// SPDX-License-Identifier: GPL-2.0 /* * Copyright IBM Corporation, 2021 * * Author: Mike Rapoport <rppt@linux.ibm.com> */ #include <linux/mm.h> #include <linux/fs.h> #include <linux/swap.h> #include <linux/mount.h> #include <linux/memfd.h> #include <linux/bitops.h> #include <linux/printk.h> #include <linux/pagemap.h> #include <linux/syscalls.h> #include <linux/pseudo_fs.h> #include <linux/secretmem.h> #include <linux/set_memory.h> #include <linux/sched/signal.h> #include <uapi/linux/magic.h> #include <asm/tlbflush.h> #include "internal.h" #undef pr_fmt #define pr_fmt(fmt) "secretmem: " fmt /* * Define mode and flag masks to allow validation of the system call * parameters. */ #define SECRETMEM_MODE_MASK (0x0) #define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK static bool secretmem_enable __ro_after_init; module_param_named(enable, secretmem_enable, bool, 0400); MODULE_PARM_DESC(secretmem_enable, "Enable secretmem and memfd_secret(2) system call"); static atomic_t secretmem_users; bool secretmem_active(void) { return !!atomic_read(&secretmem_users); } static vm_fault_t secretmem_fault(struct vm_fault *vmf) { struct address_space *mapping = vmf->vma->vm_file->f_mapping; struct inode *inode = file_inode(vmf->vma->vm_file); pgoff_t offset = vmf->pgoff; gfp_t gfp = vmf->gfp_mask; unsigned long addr; struct page *page; int err; if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) return vmf_error(-EINVAL); retry: page = find_lock_page(mapping, offset); if (!page) { page = alloc_page(gfp | __GFP_ZERO); if (!page) return VM_FAULT_OOM; err = set_direct_map_invalid_noflush(page); if (err) { put_page(page); return vmf_error(err); } __SetPageUptodate(page); err = add_to_page_cache_lru(page, mapping, offset, gfp); if (unlikely(err)) { put_page(page); /* * If a split of large page was required, it * already happened when we marked the page invalid * which guarantees that this call won't fail */ set_direct_map_default_noflush(page); if (err == -EEXIST) goto retry; return vmf_error(err); } addr = (unsigned long)page_address(page); flush_tlb_kernel_range(addr, addr + PAGE_SIZE); } vmf->page = page; return VM_FAULT_LOCKED; } static const struct vm_operations_struct secretmem_vm_ops = { .fault = secretmem_fault, }; static int secretmem_release(struct inode *inode, struct file *file) { atomic_dec(&secretmem_users); return 0; } static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) { unsigned long len = vma->vm_end - vma->vm_start; if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) return -EINVAL; if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) return -EAGAIN; vma->vm_flags |= VM_LOCKED | VM_DONTDUMP; vma->vm_ops = &secretmem_vm_ops; return 0; } bool vma_is_secretmem(struct vm_area_struct *vma) { return vma->vm_ops == &secretmem_vm_ops; } static const struct file_operations secretmem_fops = { .release = secretmem_release, .mmap = secretmem_mmap, }; static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode) { return false; } static int secretmem_migratepage(struct address_space *mapping, struct page *newpage, struct page *page, enum migrate_mode mode) { return -EBUSY; } static void secretmem_freepage(struct page *page) { set_direct_map_default_noflush(page); clear_highpage(page); } const struct address_space_operations secretmem_aops = { .set_page_dirty = __set_page_dirty_no_writeback, .freepage = secretmem_freepage, .migratepage = secretmem_migratepage, .isolate_page = secretmem_isolate_page, }; static struct vfsmount *secretmem_mnt; static struct file *secretmem_file_create(unsigned long flags) { struct file *file = ERR_PTR(-ENOMEM); struct inode *inode; inode = alloc_anon_inode(secretmem_mnt->mnt_sb); if (IS_ERR(inode)) return ERR_CAST(inode); file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", O_RDWR, &secretmem_fops); if (IS_ERR(file)) goto err_free_inode; mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); mapping_set_unevictable(inode->i_mapping); inode->i_mapping->a_ops = &secretmem_aops; /* pretend we are a normal file with zero size */ inode->i_mode |= S_IFREG; inode->i_size = 0; return file; err_free_inode: iput(inode); return file; } SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) { struct file *file; int fd, err; /* make sure local flags do not confict with global fcntl.h */ BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); if (!secretmem_enable) return -ENOSYS; if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) return -EINVAL; if (atomic_read(&secretmem_users) < 0) return -ENFILE; fd = get_unused_fd_flags(flags & O_CLOEXEC); if (fd < 0) return fd; file = secretmem_file_create(flags); if (IS_ERR(file)) { err = PTR_ERR(file); goto err_put_fd; } file->f_flags |= O_LARGEFILE; atomic_inc(&secretmem_users); fd_install(fd, file); return fd; err_put_fd: put_unused_fd(fd); return err; } static int secretmem_init_fs_context(struct fs_context *fc) { return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM; } static struct file_system_type secretmem_fs = { .name = "secretmem", .init_fs_context = secretmem_init_fs_context, .kill_sb = kill_anon_super, }; static int secretmem_init(void) { int ret = 0; if (!secretmem_enable) return ret; secretmem_mnt = kern_mount(&secretmem_fs); if (IS_ERR(secretmem_mnt)) ret = PTR_ERR(secretmem_mnt); /* prevent secretmem mappings from ever getting PROT_EXEC */ secretmem_mnt->mnt_flags |= MNT_NOEXEC; return ret; } fs_initcall(secretmem_init);