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 folio *folio; 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 folio = filemap_lock_folio(mapping, offset); 68 if (IS_ERR(folio)) { 69 folio = folio_alloc(gfp | __GFP_ZERO, 0); 70 if (!folio) { 71 ret = VM_FAULT_OOM; 72 goto out; 73 } 74 75 err = set_direct_map_invalid_noflush(folio_page(folio, 0)); 76 if (err) { 77 folio_put(folio); 78 ret = vmf_error(err); 79 goto out; 80 } 81 82 __folio_mark_uptodate(folio); 83 err = filemap_add_folio(mapping, folio, offset, gfp); 84 if (unlikely(err)) { 85 folio_put(folio); 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(folio_page(folio, 0)); 92 if (err == -EEXIST) 93 goto retry; 94 95 ret = vmf_error(err); 96 goto out; 97 } 98 99 addr = (unsigned long)folio_address(folio); 100 flush_tlb_kernel_range(addr, addr + PAGE_SIZE); 101 } 102 103 vmf->page = folio_file_page(folio, vmf->pgoff); 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_prepare(struct vm_area_desc *desc) 122 { 123 const unsigned long len = desc->end - desc->start; 124 125 if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0) 126 return -EINVAL; 127 128 if (!mlock_future_ok(desc->mm, desc->vm_flags | VM_LOCKED, len)) 129 return -EAGAIN; 130 131 desc->vm_flags |= VM_LOCKED | VM_DONTDUMP; 132 desc->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_prepare = secretmem_mmap_prepare, 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(folio, 0)); 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]"; 196 197 inode = anon_inode_make_secure_inode(secretmem_mnt->mnt_sb, anon_name, NULL); 198 if (IS_ERR(inode)) 199 return ERR_CAST(inode); 200 201 file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", 202 O_RDWR | O_LARGEFILE, &secretmem_fops); 203 if (IS_ERR(file)) 204 goto err_free_inode; 205 206 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 207 mapping_set_unevictable(inode->i_mapping); 208 209 inode->i_op = &secretmem_iops; 210 inode->i_mapping->a_ops = &secretmem_aops; 211 212 /* pretend we are a normal file with zero size */ 213 inode->i_mode |= S_IFREG; 214 inode->i_size = 0; 215 216 atomic_inc(&secretmem_users); 217 218 return file; 219 220 err_free_inode: 221 iput(inode); 222 return file; 223 } 224 225 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) 226 { 227 struct file *file; 228 int fd, err; 229 230 /* make sure local flags do not confict with global fcntl.h */ 231 BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); 232 233 if (!secretmem_enable || !can_set_direct_map()) 234 return -ENOSYS; 235 236 if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) 237 return -EINVAL; 238 if (atomic_read(&secretmem_users) < 0) 239 return -ENFILE; 240 241 fd = get_unused_fd_flags(flags & O_CLOEXEC); 242 if (fd < 0) 243 return fd; 244 245 file = secretmem_file_create(flags); 246 if (IS_ERR(file)) { 247 err = PTR_ERR(file); 248 goto err_put_fd; 249 } 250 251 fd_install(fd, file); 252 return fd; 253 254 err_put_fd: 255 put_unused_fd(fd); 256 return err; 257 } 258 259 static int secretmem_init_fs_context(struct fs_context *fc) 260 { 261 struct pseudo_fs_context *ctx; 262 263 ctx = init_pseudo(fc, SECRETMEM_MAGIC); 264 if (!ctx) 265 return -ENOMEM; 266 267 fc->s_iflags |= SB_I_NOEXEC; 268 fc->s_iflags |= SB_I_NODEV; 269 return 0; 270 } 271 272 static struct file_system_type secretmem_fs = { 273 .name = "secretmem", 274 .init_fs_context = secretmem_init_fs_context, 275 .kill_sb = kill_anon_super, 276 }; 277 278 static int __init secretmem_init(void) 279 { 280 if (!secretmem_enable || !can_set_direct_map()) 281 return 0; 282 283 secretmem_mnt = kern_mount(&secretmem_fs); 284 if (IS_ERR(secretmem_mnt)) 285 return PTR_ERR(secretmem_mnt); 286 287 return 0; 288 } 289 fs_initcall(secretmem_init); 290