diff options
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/mem.c | 101 |
1 files changed, 99 insertions, 2 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 43dd0891ca1e..31cae88a730b 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -31,11 +31,15 @@ #include <linux/uio.h> #include <linux/uaccess.h> #include <linux/security.h> +#include <linux/pseudo_fs.h> +#include <uapi/linux/magic.h> +#include <linux/mount.h> #ifdef CONFIG_IA64 # include <linux/efi.h> #endif +#define DEVMEM_MINOR 1 #define DEVPORT_MINOR 4 static inline unsigned long size_inside_page(unsigned long start, @@ -805,12 +809,64 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig) return ret; } +static struct inode *devmem_inode; + +#ifdef CONFIG_IO_STRICT_DEVMEM +void revoke_devmem(struct resource *res) +{ + struct inode *inode = READ_ONCE(devmem_inode); + + /* + * Check that the initialization has completed. Losing the race + * is ok because it means drivers are claiming resources before + * the fs_initcall level of init and prevent /dev/mem from + * establishing mappings. + */ + if (!inode) + return; + + /* + * The expectation is that the driver has successfully marked + * the resource busy by this point, so devmem_is_allowed() + * should start returning false, however for performance this + * does not iterate the entire resource range. + */ + if (devmem_is_allowed(PHYS_PFN(res->start)) && + devmem_is_allowed(PHYS_PFN(res->end))) { + /* + * *cringe* iomem=relaxed says "go ahead, what's the + * worst that can happen?" + */ + return; + } + + unmap_mapping_range(inode->i_mapping, res->start, resource_size(res), 1); +} +#endif + static int open_port(struct inode *inode, struct file *filp) { + int rc; + if (!capable(CAP_SYS_RAWIO)) return -EPERM; - return security_locked_down(LOCKDOWN_DEV_MEM); + rc = security_locked_down(LOCKDOWN_DEV_MEM); + if (rc) + return rc; + + if (iminor(inode) != DEVMEM_MINOR) + return 0; + + /* + * Use a unified address space to have a single point to manage + * revocations when drivers want to take over a /dev/mem mapped + * range. + */ + inode->i_mapping = devmem_inode->i_mapping; + filp->f_mapping = inode->i_mapping; + + return 0; } #define zero_lseek null_lseek @@ -885,7 +941,7 @@ static const struct memdev { fmode_t fmode; } devlist[] = { #ifdef CONFIG_DEVMEM - [1] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET }, + [DEVMEM_MINOR] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET }, #endif #ifdef CONFIG_DEVKMEM [2] = { "kmem", 0, &kmem_fops, FMODE_UNSIGNED_OFFSET }, @@ -939,6 +995,45 @@ static char *mem_devnode(struct device *dev, umode_t *mode) static struct class *mem_class; +static int devmem_fs_init_fs_context(struct fs_context *fc) +{ + return init_pseudo(fc, DEVMEM_MAGIC) ? 0 : -ENOMEM; +} + +static struct file_system_type devmem_fs_type = { + .name = "devmem", + .owner = THIS_MODULE, + .init_fs_context = devmem_fs_init_fs_context, + .kill_sb = kill_anon_super, +}; + +static int devmem_init_inode(void) +{ + static struct vfsmount *devmem_vfs_mount; + static int devmem_fs_cnt; + struct inode *inode; + int rc; + + rc = simple_pin_fs(&devmem_fs_type, &devmem_vfs_mount, &devmem_fs_cnt); + if (rc < 0) { + pr_err("Cannot mount /dev/mem pseudo filesystem: %d\n", rc); + return rc; + } + + inode = alloc_anon_inode(devmem_vfs_mount->mnt_sb); + if (IS_ERR(inode)) { + rc = PTR_ERR(inode); + pr_err("Cannot allocate inode for /dev/mem: %d\n", rc); + simple_release_fs(&devmem_vfs_mount, &devmem_fs_cnt); + return rc; + } + + /* publish /dev/mem initialized */ + WRITE_ONCE(devmem_inode, inode); + + return 0; +} + static int __init chr_dev_init(void) { int minor; @@ -960,6 +1055,8 @@ static int __init chr_dev_init(void) */ if ((minor == DEVPORT_MINOR) && !arch_has_dev_port()) continue; + if ((minor == DEVMEM_MINOR) && devmem_init_inode() != 0) + continue; device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor), NULL, devlist[minor].name); |