Merge tag 'regmap-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie...
[linux-2.6-microblaze.git] / mm / secretmem.c
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         .set_page_dirty = __set_page_dirty_no_writeback,
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);