1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright IBM Corporation, 2021 4 * 5 * Author: Mike Rapoport <rppt@linux.ibm.com> 6 */ 7 8 #include <linux/mm.h> 9 #include <linux/fs.h> 10 #include <linux/swap.h> 11 #include <linux/mount.h> 12 #include <linux/memfd.h> 13 #include <linux/bitops.h> 14 #include <linux/printk.h> 15 #include <linux/pagemap.h> 16 #include <linux/syscalls.h> 17 #include <linux/pseudo_fs.h> 18 #include <linux/secretmem.h> 19 #include <linux/set_memory.h> 20 #include <linux/sched/signal.h> 21 22 #include <uapi/linux/magic.h> 23 24 #include <asm/tlbflush.h> 25 26 #include "internal.h" 27 28 #undef pr_fmt 29 #define pr_fmt(fmt) "secretmem: " fmt 30 31 /* 32 * Define mode and flag masks to allow validation of the system call 33 * parameters. 34 */ 35 #define SECRETMEM_MODE_MASK (0x0) 36 #define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK 37 38 static bool secretmem_enable __ro_after_init; 39 module_param_named(enable, secretmem_enable, bool, 0400); 40 MODULE_PARM_DESC(secretmem_enable, 41 "Enable secretmem and memfd_secret(2) system call"); 42 43 static atomic_t secretmem_users; 44 45 bool secretmem_active(void) 46 { 47 return !!atomic_read(&secretmem_users); 48 } 49 50 static vm_fault_t secretmem_fault(struct vm_fault *vmf) 51 { 52 struct address_space *mapping = vmf->vma->vm_file->f_mapping; 53 struct inode *inode = file_inode(vmf->vma->vm_file); 54 pgoff_t offset = vmf->pgoff; 55 gfp_t gfp = vmf->gfp_mask; 56 unsigned long addr; 57 struct page *page; 58 int err; 59 60 if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) 61 return vmf_error(-EINVAL); 62 63 retry: 64 page = find_lock_page(mapping, offset); 65 if (!page) { 66 page = alloc_page(gfp | __GFP_ZERO); 67 if (!page) 68 return VM_FAULT_OOM; 69 70 err = set_direct_map_invalid_noflush(page); 71 if (err) { 72 put_page(page); 73 return vmf_error(err); 74 } 75 76 __SetPageUptodate(page); 77 err = add_to_page_cache_lru(page, mapping, offset, gfp); 78 if (unlikely(err)) { 79 put_page(page); 80 /* 81 * If a split of large page was required, it 82 * already happened when we marked the page invalid 83 * which guarantees that this call won't fail 84 */ 85 set_direct_map_default_noflush(page); 86 if (err == -EEXIST) 87 goto retry; 88 89 return vmf_error(err); 90 } 91 92 addr = (unsigned long)page_address(page); 93 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 94 } 95 96 vmf->page = page; 97 return VM_FAULT_LOCKED; 98 } 99 100 static const struct vm_operations_struct secretmem_vm_ops = { 101 .fault = secretmem_fault, 102 }; 103 104 static int secretmem_release(struct inode *inode, struct file *file) 105 { 106 atomic_dec(&secretmem_users); 107 return 0; 108 } 109 110 static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) 111 { 112 unsigned long len = vma->vm_end - vma->vm_start; 113 114 if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) 115 return -EINVAL; 116 117 if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) 118 return -EAGAIN; 119 120 vma->vm_flags |= VM_LOCKED | VM_DONTDUMP; 121 vma->vm_ops = &secretmem_vm_ops; 122 123 return 0; 124 } 125 126 bool vma_is_secretmem(struct vm_area_struct *vma) 127 { 128 return vma->vm_ops == &secretmem_vm_ops; 129 } 130 131 static const struct file_operations secretmem_fops = { 132 .release = secretmem_release, 133 .mmap = secretmem_mmap, 134 }; 135 136 static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode) 137 { 138 return false; 139 } 140 141 static int secretmem_migratepage(struct address_space *mapping, 142 struct page *newpage, struct page *page, 143 enum migrate_mode mode) 144 { 145 return -EBUSY; 146 } 147 148 static void secretmem_freepage(struct page *page) 149 { 150 set_direct_map_default_noflush(page); 151 clear_highpage(page); 152 } 153 154 const struct address_space_operations secretmem_aops = { 155 .dirty_folio = noop_dirty_folio, 156 .freepage = secretmem_freepage, 157 .migratepage = secretmem_migratepage, 158 .isolate_page = secretmem_isolate_page, 159 }; 160 161 static struct vfsmount *secretmem_mnt; 162 163 static struct file *secretmem_file_create(unsigned long flags) 164 { 165 struct file *file = ERR_PTR(-ENOMEM); 166 struct inode *inode; 167 168 inode = alloc_anon_inode(secretmem_mnt->mnt_sb); 169 if (IS_ERR(inode)) 170 return ERR_CAST(inode); 171 172 file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", 173 O_RDWR, &secretmem_fops); 174 if (IS_ERR(file)) 175 goto err_free_inode; 176 177 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 178 mapping_set_unevictable(inode->i_mapping); 179 180 inode->i_mapping->a_ops = &secretmem_aops; 181 182 /* pretend we are a normal file with zero size */ 183 inode->i_mode |= S_IFREG; 184 inode->i_size = 0; 185 186 return file; 187 188 err_free_inode: 189 iput(inode); 190 return file; 191 } 192 193 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) 194 { 195 struct file *file; 196 int fd, err; 197 198 /* make sure local flags do not confict with global fcntl.h */ 199 BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); 200 201 if (!secretmem_enable) 202 return -ENOSYS; 203 204 if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) 205 return -EINVAL; 206 if (atomic_read(&secretmem_users) < 0) 207 return -ENFILE; 208 209 fd = get_unused_fd_flags(flags & O_CLOEXEC); 210 if (fd < 0) 211 return fd; 212 213 file = secretmem_file_create(flags); 214 if (IS_ERR(file)) { 215 err = PTR_ERR(file); 216 goto err_put_fd; 217 } 218 219 file->f_flags |= O_LARGEFILE; 220 221 atomic_inc(&secretmem_users); 222 fd_install(fd, file); 223 return fd; 224 225 err_put_fd: 226 put_unused_fd(fd); 227 return err; 228 } 229 230 static int secretmem_init_fs_context(struct fs_context *fc) 231 { 232 return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM; 233 } 234 235 static struct file_system_type secretmem_fs = { 236 .name = "secretmem", 237 .init_fs_context = secretmem_init_fs_context, 238 .kill_sb = kill_anon_super, 239 }; 240 241 static int secretmem_init(void) 242 { 243 int ret = 0; 244 245 if (!secretmem_enable) 246 return ret; 247 248 secretmem_mnt = kern_mount(&secretmem_fs); 249 if (IS_ERR(secretmem_mnt)) 250 ret = PTR_ERR(secretmem_mnt); 251 252 /* prevent secretmem mappings from ever getting PROT_EXEC */ 253 secretmem_mnt->mnt_flags |= MNT_NOEXEC; 254 255 return ret; 256 } 257 fs_initcall(secretmem_init); 258