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