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 /* 86 * If a split of large page was required, it 87 * already happened when we marked the page invalid 88 * which guarantees that this call won't fail 89 */ 90 set_direct_map_default_noflush(folio_page(folio, 0)); 91 folio_put(folio); 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 = vma_desc_size(desc); 124 125 if (!vma_desc_test_flags(desc, VMA_SHARED_BIT, VMA_MAYSHARE_BIT)) 126 return -EINVAL; 127 128 vma_desc_set_flags(desc, VMA_LOCKED_BIT, VMA_DONTDUMP_BIT); 129 if (!mlock_future_ok(desc->mm, /*is_vma_locked=*/ true, len)) 130 return -EAGAIN; 131 desc->vm_ops = &secretmem_vm_ops; 132 133 return 0; 134 } 135 136 bool vma_is_secretmem(struct vm_area_struct *vma) 137 { 138 return vma->vm_ops == &secretmem_vm_ops; 139 } 140 141 static const struct file_operations secretmem_fops = { 142 .release = secretmem_release, 143 .mmap_prepare = secretmem_mmap_prepare, 144 }; 145 146 static int secretmem_migrate_folio(struct address_space *mapping, 147 struct folio *dst, struct folio *src, enum migrate_mode mode) 148 { 149 return -EBUSY; 150 } 151 152 static void secretmem_free_folio(struct folio *folio) 153 { 154 set_direct_map_default_noflush(folio_page(folio, 0)); 155 folio_zero_segment(folio, 0, folio_size(folio)); 156 } 157 158 const struct address_space_operations secretmem_aops = { 159 .dirty_folio = noop_dirty_folio, 160 .free_folio = secretmem_free_folio, 161 .migrate_folio = secretmem_migrate_folio, 162 }; 163 164 static int secretmem_setattr(struct mnt_idmap *idmap, 165 struct dentry *dentry, struct iattr *iattr) 166 { 167 struct inode *inode = d_inode(dentry); 168 struct address_space *mapping = inode->i_mapping; 169 unsigned int ia_valid = iattr->ia_valid; 170 int ret; 171 172 filemap_invalidate_lock(mapping); 173 174 if ((ia_valid & ATTR_SIZE) && inode->i_size) 175 ret = -EINVAL; 176 else 177 ret = simple_setattr(idmap, dentry, iattr); 178 179 filemap_invalidate_unlock(mapping); 180 181 return ret; 182 } 183 184 static const struct inode_operations secretmem_iops = { 185 .setattr = secretmem_setattr, 186 }; 187 188 static struct vfsmount *secretmem_mnt; 189 190 static struct file *secretmem_file_create(unsigned long flags) 191 { 192 struct file *file; 193 struct inode *inode; 194 const char *anon_name = "[secretmem]"; 195 196 inode = anon_inode_make_secure_inode(secretmem_mnt->mnt_sb, anon_name, NULL); 197 if (IS_ERR(inode)) 198 return ERR_CAST(inode); 199 200 file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem", 201 O_RDWR | O_LARGEFILE, &secretmem_fops); 202 if (IS_ERR(file)) 203 goto err_free_inode; 204 205 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); 206 mapping_set_unevictable(inode->i_mapping); 207 208 inode->i_op = &secretmem_iops; 209 inode->i_mapping->a_ops = &secretmem_aops; 210 211 /* pretend we are a normal file with zero size */ 212 inode->i_mode |= S_IFREG; 213 inode->i_size = 0; 214 215 atomic_inc(&secretmem_users); 216 217 return file; 218 219 err_free_inode: 220 iput(inode); 221 return file; 222 } 223 224 SYSCALL_DEFINE1(memfd_secret, unsigned int, flags) 225 { 226 /* make sure local flags do not conflict with global fcntl.h */ 227 BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC); 228 229 if (!secretmem_enable || !can_set_direct_map()) 230 return -ENOSYS; 231 232 if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC)) 233 return -EINVAL; 234 if (atomic_read(&secretmem_users) < 0) 235 return -ENFILE; 236 237 return FD_ADD(flags & O_CLOEXEC, secretmem_file_create(flags)); 238 } 239 240 static int secretmem_init_fs_context(struct fs_context *fc) 241 { 242 struct pseudo_fs_context *ctx; 243 244 ctx = init_pseudo(fc, SECRETMEM_MAGIC); 245 if (!ctx) 246 return -ENOMEM; 247 248 fc->s_iflags |= SB_I_NOEXEC; 249 fc->s_iflags |= SB_I_NODEV; 250 return 0; 251 } 252 253 static struct file_system_type secretmem_fs = { 254 .name = "secretmem", 255 .init_fs_context = secretmem_init_fs_context, 256 .kill_sb = kill_anon_super, 257 }; 258 259 static int __init secretmem_init(void) 260 { 261 if (!secretmem_enable || !can_set_direct_map()) 262 return 0; 263 264 secretmem_mnt = kern_mount(&secretmem_fs); 265 if (IS_ERR(secretmem_mnt)) 266 return PTR_ERR(secretmem_mnt); 267 268 return 0; 269 } 270 fs_initcall(secretmem_init); 271