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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright IBM Corporation, 2021
*
* Author: Mike Rapoport <rppt@linux.ibm.com>
*/
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/swap.h>
#include <linux/mount.h>
#include <linux/memfd.h>
#include <linux/bitops.h>
#include <linux/printk.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/pseudo_fs.h>
#include <linux/secretmem.h>
#include <linux/set_memory.h>
#include <linux/sched/signal.h>
#include <uapi/linux/magic.h>
#include <asm/tlbflush.h>
#include "internal.h"
#undef pr_fmt
#define pr_fmt(fmt) "secretmem: " fmt
/*
* Define mode and flag masks to allow validation of the system call
* parameters.
*/
#define SECRETMEM_MODE_MASK (0x0)
#define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK
static bool secretmem_enable __ro_after_init;
module_param_named(enable, secretmem_enable, bool, 0400);
MODULE_PARM_DESC(secretmem_enable,
"Enable secretmem and memfd_secret(2) system call");
static vm_fault_t secretmem_fault(struct vm_fault *vmf)
{
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
struct inode *inode = file_inode(vmf->vma->vm_file);
pgoff_t offset = vmf->pgoff;
gfp_t gfp = vmf->gfp_mask;
unsigned long addr;
struct page *page;
int err;
if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
return vmf_error(-EINVAL);
retry:
page = find_lock_page(mapping, offset);
if (!page) {
page = alloc_page(gfp | __GFP_ZERO);
if (!page)
return VM_FAULT_OOM;
err = set_direct_map_invalid_noflush(page);
if (err) {
put_page(page);
return vmf_error(err);
}
__SetPageUptodate(page);
err = add_to_page_cache_lru(page, mapping, offset, gfp);
if (unlikely(err)) {
put_page(page);
/*
* If a split of large page was required, it
* already happened when we marked the page invalid
* which guarantees that this call won't fail
*/
set_direct_map_default_noflush(page);
if (err == -EEXIST)
goto retry;
return vmf_error(err);
}
addr = (unsigned long)page_address(page);
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
}
vmf->page = page;
return VM_FAULT_LOCKED;
}
static const struct vm_operations_struct secretmem_vm_ops = {
.fault = secretmem_fault,
};
static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
{
unsigned long len = vma->vm_end - vma->vm_start;
if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
return -EINVAL;
if (mlock_future_check(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
return -EAGAIN;
vma->vm_flags |= VM_LOCKED | VM_DONTDUMP;
vma->vm_ops = &secretmem_vm_ops;
return 0;
}
bool vma_is_secretmem(struct vm_area_struct *vma)
{
return vma->vm_ops == &secretmem_vm_ops;
}
static const struct file_operations secretmem_fops = {
.mmap = secretmem_mmap,
};
static bool secretmem_isolate_page(struct page *page, isolate_mode_t mode)
{
return false;
}
static int secretmem_migratepage(struct address_space *mapping,
struct page *newpage, struct page *page,
enum migrate_mode mode)
{
return -EBUSY;
}
static void secretmem_freepage(struct page *page)
{
set_direct_map_default_noflush(page);
clear_highpage(page);
}
const struct address_space_operations secretmem_aops = {
.freepage = secretmem_freepage,
.migratepage = secretmem_migratepage,
.isolate_page = secretmem_isolate_page,
};
static struct vfsmount *secretmem_mnt;
static struct file *secretmem_file_create(unsigned long flags)
{
struct file *file = ERR_PTR(-ENOMEM);
struct inode *inode;
inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
if (IS_ERR(inode))
return ERR_CAST(inode);
file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
O_RDWR, &secretmem_fops);
if (IS_ERR(file))
goto err_free_inode;
mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
mapping_set_unevictable(inode->i_mapping);
inode->i_mapping->a_ops = &secretmem_aops;
/* pretend we are a normal file with zero size */
inode->i_mode |= S_IFREG;
inode->i_size = 0;
return file;
err_free_inode:
iput(inode);
return file;
}
SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
{
struct file *file;
int fd, err;
/* make sure local flags do not confict with global fcntl.h */
BUILD_BUG_ON(SECRETMEM_FLAGS_MASK & O_CLOEXEC);
if (!secretmem_enable)
return -ENOSYS;
if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC))
return -EINVAL;
fd = get_unused_fd_flags(flags & O_CLOEXEC);
if (fd < 0)
return fd;
file = secretmem_file_create(flags);
if (IS_ERR(file)) {
err = PTR_ERR(file);
goto err_put_fd;
}
file->f_flags |= O_LARGEFILE;
fd_install(fd, file);
return fd;
err_put_fd:
put_unused_fd(fd);
return err;
}
static int secretmem_init_fs_context(struct fs_context *fc)
{
return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM;
}
static struct file_system_type secretmem_fs = {
.name = "secretmem",
.init_fs_context = secretmem_init_fs_context,
.kill_sb = kill_anon_super,
};
static int secretmem_init(void)
{
int ret = 0;
if (!secretmem_enable)
return ret;
secretmem_mnt = kern_mount(&secretmem_fs);
if (IS_ERR(secretmem_mnt))
ret = PTR_ERR(secretmem_mnt);
/* prevent secretmem mappings from ever getting PROT_EXEC */
secretmem_mnt->mnt_flags |= MNT_NOEXEC;
return ret;
}
fs_initcall(secretmem_init);
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