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 = 1; 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 struct folio *folio; 59 vm_fault_t ret; 60 int err; 61 62 if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) 63 return vmf_error(-EINVAL); 64 65 filemap_invalidate_lock_shared(mapping); 66 67 retry: 68 page = find_lock_page(mapping, offset); 69 if (!page) { 70 folio = folio_alloc(gfp | __GFP_ZERO, 0); 71 if (!folio) { 72 ret = VM_FAULT_OOM; 73 goto out; 74 } 75 76 page = &folio->page; 77 err = set_direct_map_invalid_noflush(page); 78 if (err) { 79 folio_put(folio); 80 ret = vmf_error(err); 81 goto out; 82 } 83 84 __folio_mark_uptodate(folio); 85 err = filemap_add_folio(mapping, folio, offset, gfp); 86 if (unlikely(err)) { 87 folio_put(folio); 88 /* 89 * If a split of large page was required, it 90 * already happened when we marked the page invalid 91 * which guarantees that this call won't fail 92 */ 93 set_direct_map_default_noflush(page); 94 if (err == -EEXIST) 95 goto retry; 96 97 ret = vmf_error(err); 98 goto out; 99 } 100 101 addr = (unsigned long)page_address(page); 102 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 103 } 104 105 vmf->page = page; 106 ret = VM_FAULT_LOCKED; 107 108 out: 109 filemap_invalidate_unlock_shared(mapping); 110 return ret; 111 } 112 113 static const struct vm_operations_struct secretmem_vm_ops = { 114 .fault = secretmem_fault, 115 }; 116 117 static int secretmem_release(struct inode *inode, struct file *file) 118 { 119 atomic_dec(&secretmem_users); 120 return 0; 121 } 122 123 static int secretmem_mmap(struct file *file, struct vm_area_struct *vma) 124 { 125 unsigned long len = vma->vm_end - vma->vm_start; 126 127 if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) 128 return -EINVAL; 129 130 if (!mlock_future_ok(vma->vm_mm, vma->vm_flags | VM_LOCKED, len)) 131 return -EAGAIN; 132 133 vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP); 134 vma->vm_ops = &secretmem_vm_ops; 135 136 return 0; 137 } 138 139 bool vma_is_secretmem(struct vm_area_struct *vma) 140 { 141 return vma->vm_ops == &secretmem_vm_ops; 142 } 143 144 static const struct file_operations secretmem_fops = { 145 .release = secretmem_release, 146 .mmap = secretmem_mmap, 147 }; 148 149 static int secretmem_migrate_folio(struct address_space *mapping, 150 struct folio *dst, struct folio *src, enum migrate_mode mode) 151 { 152 return -EBUSY; 153 } 154 155 static void secretmem_free_folio(struct folio *folio) 156 { 157 set_direct_map_default_noflush(&folio->page); 158 folio_zero_segment(folio, 0, folio_size(folio)); 159 } 160 161 const struct address_space_operations secretmem_aops = { 162 .dirty_folio = noop_dirty_folio, 163 .free_folio = secretmem_free_folio, 164 .migrate_folio = secretmem_migrate_folio, 165 }; 166 167 static int secretmem_setattr(struct mnt_idmap *idmap, 168 struct dentry *dentry, struct iattr *iattr) 169 { 170 struct inode *inode = d_inode(dentry); 171 struct address_space *mapping = inode->i_mapping; 172 unsigned int ia_valid = iattr->ia_valid; 173 int ret; 174 175 filemap_invalidate_lock(mapping); 176 177 if ((ia_valid & ATTR_SIZE) && inode->i_size) 178 ret = -EINVAL; 179 else 180 ret = simple_setattr(idmap, dentry, iattr); 181 182 filemap_invalidate_unlock(mapping); 183 184 return ret; 185 } 186 187 static const struct inode_operations secretmem_iops = { 188 .setattr = secretmem_setattr, 189 }; 190 191 static struct vfsmount *secretmem_mnt; 192 193 static struct file *secretmem_file_create(unsigned long flags) 194 { 195 struct file *file; 196 struct inode *inode; 197 const char *anon_name = "[secretmem]"; 198 const struct qstr qname = QSTR_INIT(anon_name, strlen(anon_name)); 199 int err; 200 201 inode = alloc_anon_inode(secretmem_mnt->mnt_sb); 202 if (IS_ERR(inode)) 203 return ERR_CAST(inode); 204 205 err = security_inode_init_security_anon(inode, &qname, NULL); 206 if (err) { 207 file = ERR_PTR(err); 208 goto err_free_inode; 209 } 210 211 file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", 212 O_RDWR, &secretmem_fops); 213 if (IS_ERR(file)) 214 goto err_free_inode; 215 216 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 217 mapping_set_unevictable(inode->i_mapping); 218 219 inode->i_op = &secretmem_iops; 220 inode->i_mapping->a_ops = &secretmem_aops; 221 222 /* pretend we are a normal file with zero size */ 223 inode->i_mode |= S_IFREG; 224 inode->i_size = 0; 225 226 return file; 227 228 err_free_inode: 229 iput(inode); 230 return file; 231 } 232 233 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) 234 { 235 struct file *file; 236 int fd, err; 237 238 /* make sure local flags do not confict with global fcntl.h */ 239 BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); 240 241 if (!secretmem_enable) 242 return -ENOSYS; 243 244 if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) 245 return -EINVAL; 246 if (atomic_read(&secretmem_users) < 0) 247 return -ENFILE; 248 249 fd = get_unused_fd_flags(flags & O_CLOEXEC); 250 if (fd < 0) 251 return fd; 252 253 file = secretmem_file_create(flags); 254 if (IS_ERR(file)) { 255 err = PTR_ERR(file); 256 goto err_put_fd; 257 } 258 259 file->f_flags |= O_LARGEFILE; 260 261 atomic_inc(&secretmem_users); 262 fd_install(fd, file); 263 return fd; 264 265 err_put_fd: 266 put_unused_fd(fd); 267 return err; 268 } 269 270 static int secretmem_init_fs_context(struct fs_context *fc) 271 { 272 return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM; 273 } 274 275 static struct file_system_type secretmem_fs = { 276 .name = "secretmem", 277 .init_fs_context = secretmem_init_fs_context, 278 .kill_sb = kill_anon_super, 279 }; 280 281 static int __init secretmem_init(void) 282 { 283 if (!secretmem_enable) 284 return 0; 285 286 secretmem_mnt = kern_mount(&secretmem_fs); 287 if (IS_ERR(secretmem_mnt)) 288 return PTR_ERR(secretmem_mnt); 289 290 /* prevent secretmem mappings from ever getting PROT_EXEC */ 291 secretmem_mnt->mnt_flags |= MNT_NOEXEC; 292 293 return 0; 294 } 295 fs_initcall(secretmem_init); 296