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linux/block/bdev.c
Deven Bowers b55d26bd18 block,lsm: add LSM blob and new LSM hooks for block devices 
This patch introduces a new LSM blob to the block_device structure,
enabling the security subsystem to store security-sensitive data related
to block devices. Currently, for a device mapper's mapped device containing
a dm-verity target, critical security information such as the roothash and
its signing state are not readily accessible. Specifically, while the
dm-verity volume creation process passes the dm-verity roothash and its
signature from userspace to the kernel, the roothash is stored privately
within the dm-verity target, and its signature is discarded
post-verification. This makes it extremely hard for the security subsystem
to utilize these data.

With the addition of the LSM blob to the block_device structure, the
security subsystem can now retain and manage important security metadata
such as the roothash and the signing state of a dm-verity by storing them
inside the blob. Access decisions can then be based on these stored data.

The implementation follows the same approach used for security blobs in
other structures like struct file, struct inode, and struct superblock.
The initialization of the security blob occurs after the creation of the
struct block_device, performed by the security subsystem. Similarly, the
security blob is freed by the security subsystem before the struct
block_device is deallocated or freed.

This patch also introduces a new hook security_bdev_setintegrity() to save
block device's integrity data to the new LSM blob. For example, for
dm-verity, it can use this hook to expose its roothash and signing state
to LSMs, then LSMs can save these data into the LSM blob.

Please note that the new hook should be invoked every time the security
information is updated to keep these data current. For example, in
dm-verity, if the mapping table is reloaded and configured to use a
different dm-verity target with a new roothash and signing information,
the previously stored data in the LSM blob will become obsolete. It is
crucial to re-invoke the hook to refresh these data and ensure they are up
to date. This necessity arises from the design of device-mapper, where a
device-mapper device is first created, and then targets are subsequently
loaded into it. These targets can be modified multiple times during the
device's lifetime. Therefore, while the LSM blob is allocated during the
creation of the block device, its actual contents are not initialized at
this stage and can change substantially over time. This includes
alterations from data that the LSM 'trusts' to those it does not, making
it essential to handle these changes correctly. Failure to address this
dynamic aspect could potentially allow for bypassing LSM checks.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
[PM: merge fuzz, subject line tweaks]
Signed-off-by: Paul Moore <paul@paul-moore.com>
2024-08-20 14:02:33 -04:00

1330 lines
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright (C) 2016 - 2020 Christoph Hellwig
*/
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/device_cgroup.h>
#include <linux/blkdev.h>
#include <linux/blk-integrity.h>
#include <linux/backing-dev.h>
#include <linux/module.h>
#include <linux/blkpg.h>
#include <linux/magic.h>
#include <linux/buffer_head.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/uio.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/part_stat.h>
#include <linux/uaccess.h>
#include <linux/stat.h>
#include "../fs/internal.h"
#include "blk.h"
/* Should we allow writing to mounted block devices? */
static bool bdev_allow_write_mounted = IS_ENABLED(CONFIG_BLK_DEV_WRITE_MOUNTED);
struct bdev_inode {
struct block_device bdev;
struct inode vfs_inode;
};
static inline struct bdev_inode *BDEV_I(struct inode *inode)
{
return container_of(inode, struct bdev_inode, vfs_inode);
}
static inline struct inode *BD_INODE(struct block_device *bdev)
{
return &container_of(bdev, struct bdev_inode, bdev)->vfs_inode;
}
struct block_device *I_BDEV(struct inode *inode)
{
return &BDEV_I(inode)->bdev;
}
EXPORT_SYMBOL(I_BDEV);
struct block_device *file_bdev(struct file *bdev_file)
{
return I_BDEV(bdev_file->f_mapping->host);
}
EXPORT_SYMBOL(file_bdev);
static void bdev_write_inode(struct block_device *bdev)
{
struct inode *inode = BD_INODE(bdev);
int ret;
spin_lock(&inode->i_lock);
while (inode->i_state & I_DIRTY) {
spin_unlock(&inode->i_lock);
ret = write_inode_now(inode, true);
if (ret)
pr_warn_ratelimited(
"VFS: Dirty inode writeback failed for block device %pg (err=%d).\n",
bdev, ret);
spin_lock(&inode->i_lock);
}
spin_unlock(&inode->i_lock);
}
/* Kill _all_ buffers and pagecache , dirty or not.. */
static void kill_bdev(struct block_device *bdev)
{
struct address_space *mapping = bdev->bd_mapping;
if (mapping_empty(mapping))
return;
invalidate_bh_lrus();
truncate_inode_pages(mapping, 0);
}
/* Invalidate clean unused buffers and pagecache. */
void invalidate_bdev(struct block_device *bdev)
{
struct address_space *mapping = bdev->bd_mapping;
if (mapping->nrpages) {
invalidate_bh_lrus();
lru_add_drain_all(); /* make sure all lru add caches are flushed */
invalidate_mapping_pages(mapping, 0, -1);
}
}
EXPORT_SYMBOL(invalidate_bdev);
/*
* Drop all buffers & page cache for given bdev range. This function bails
* with error if bdev has other exclusive owner (such as filesystem).
*/
int truncate_bdev_range(struct block_device *bdev, blk_mode_t mode,
loff_t lstart, loff_t lend)
{
/*
* If we don't hold exclusive handle for the device, upgrade to it
* while we discard the buffer cache to avoid discarding buffers
* under live filesystem.
*/
if (!(mode & BLK_OPEN_EXCL)) {
int err = bd_prepare_to_claim(bdev, truncate_bdev_range, NULL);
if (err)
goto invalidate;
}
truncate_inode_pages_range(bdev->bd_mapping, lstart, lend);
if (!(mode & BLK_OPEN_EXCL))
bd_abort_claiming(bdev, truncate_bdev_range);
return 0;
invalidate:
/*
* Someone else has handle exclusively open. Try invalidating instead.
* The 'end' argument is inclusive so the rounding is safe.
*/
return invalidate_inode_pages2_range(bdev->bd_mapping,
lstart >> PAGE_SHIFT,
lend >> PAGE_SHIFT);
}
static void set_init_blocksize(struct block_device *bdev)
{
unsigned int bsize = bdev_logical_block_size(bdev);
loff_t size = i_size_read(BD_INODE(bdev));
while (bsize < PAGE_SIZE) {
if (size & bsize)
break;
bsize <<= 1;
}
BD_INODE(bdev)->i_blkbits = blksize_bits(bsize);
}
int set_blocksize(struct file *file, int size)
{
struct inode *inode = file->f_mapping->host;
struct block_device *bdev = I_BDEV(inode);
/* Size must be a power of two, and between 512 and PAGE_SIZE */
if (size > PAGE_SIZE || size < 512 || !is_power_of_2(size))
return -EINVAL;
/* Size cannot be smaller than the size supported by the device */
if (size < bdev_logical_block_size(bdev))
return -EINVAL;
if (!file->private_data)
return -EINVAL;
/* Don't change the size if it is same as current */
if (inode->i_blkbits != blksize_bits(size)) {
sync_blockdev(bdev);
inode->i_blkbits = blksize_bits(size);
kill_bdev(bdev);
}
return 0;
}
EXPORT_SYMBOL(set_blocksize);
int sb_set_blocksize(struct super_block *sb, int size)
{
if (set_blocksize(sb->s_bdev_file, size))
return 0;
/* If we get here, we know size is power of two
* and it's value is between 512 and PAGE_SIZE */
sb->s_blocksize = size;
sb->s_blocksize_bits = blksize_bits(size);
return sb->s_blocksize;
}
EXPORT_SYMBOL(sb_set_blocksize);
int sb_min_blocksize(struct super_block *sb, int size)
{
int minsize = bdev_logical_block_size(sb->s_bdev);
if (size < minsize)
size = minsize;
return sb_set_blocksize(sb, size);
}
EXPORT_SYMBOL(sb_min_blocksize);
int sync_blockdev_nowait(struct block_device *bdev)
{
if (!bdev)
return 0;
return filemap_flush(bdev->bd_mapping);
}
EXPORT_SYMBOL_GPL(sync_blockdev_nowait);
/*
* Write out and wait upon all the dirty data associated with a block
* device via its mapping. Does not take the superblock lock.
*/
int sync_blockdev(struct block_device *bdev)
{
if (!bdev)
return 0;
return filemap_write_and_wait(bdev->bd_mapping);
}
EXPORT_SYMBOL(sync_blockdev);
int sync_blockdev_range(struct block_device *bdev, loff_t lstart, loff_t lend)
{
return filemap_write_and_wait_range(bdev->bd_mapping,
lstart, lend);
}
EXPORT_SYMBOL(sync_blockdev_range);
/**
* bdev_freeze - lock a filesystem and force it into a consistent state
* @bdev: blockdevice to lock
*
* If a superblock is found on this device, we take the s_umount semaphore
* on it to make sure nobody unmounts until the snapshot creation is done.
* The reference counter (bd_fsfreeze_count) guarantees that only the last
* unfreeze process can unfreeze the frozen filesystem actually when multiple
* freeze requests arrive simultaneously. It counts up in bdev_freeze() and
* count down in bdev_thaw(). When it becomes 0, thaw_bdev() will unfreeze
* actually.
*
* Return: On success zero is returned, negative error code on failure.
*/
int bdev_freeze(struct block_device *bdev)
{
int error = 0;
mutex_lock(&bdev->bd_fsfreeze_mutex);
if (atomic_inc_return(&bdev->bd_fsfreeze_count) > 1) {
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return 0;
}
mutex_lock(&bdev->bd_holder_lock);
if (bdev->bd_holder_ops && bdev->bd_holder_ops->freeze) {
error = bdev->bd_holder_ops->freeze(bdev);
lockdep_assert_not_held(&bdev->bd_holder_lock);
} else {
mutex_unlock(&bdev->bd_holder_lock);
error = sync_blockdev(bdev);
}
if (error)
atomic_dec(&bdev->bd_fsfreeze_count);
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return error;
}
EXPORT_SYMBOL(bdev_freeze);
/**
* bdev_thaw - unlock filesystem
* @bdev: blockdevice to unlock
*
* Unlocks the filesystem and marks it writeable again after bdev_freeze().
*
* Return: On success zero is returned, negative error code on failure.
*/
int bdev_thaw(struct block_device *bdev)
{
int error = -EINVAL, nr_freeze;
mutex_lock(&bdev->bd_fsfreeze_mutex);
/*
* If this returns < 0 it means that @bd_fsfreeze_count was
* already 0 and no decrement was performed.
*/
nr_freeze = atomic_dec_if_positive(&bdev->bd_fsfreeze_count);
if (nr_freeze < 0)
goto out;
error = 0;
if (nr_freeze > 0)
goto out;
mutex_lock(&bdev->bd_holder_lock);
if (bdev->bd_holder_ops && bdev->bd_holder_ops->thaw) {
error = bdev->bd_holder_ops->thaw(bdev);
lockdep_assert_not_held(&bdev->bd_holder_lock);
} else {
mutex_unlock(&bdev->bd_holder_lock);
}
if (error)
atomic_inc(&bdev->bd_fsfreeze_count);
out:
mutex_unlock(&bdev->bd_fsfreeze_mutex);
return error;
}
EXPORT_SYMBOL(bdev_thaw);
/*
* pseudo-fs
*/
static __cacheline_aligned_in_smp DEFINE_MUTEX(bdev_lock);
static struct kmem_cache *bdev_cachep __ro_after_init;
static struct inode *bdev_alloc_inode(struct super_block *sb)
{
struct bdev_inode *ei = alloc_inode_sb(sb, bdev_cachep, GFP_KERNEL);
if (!ei)
return NULL;
memset(&ei->bdev, 0, sizeof(ei->bdev));
if (security_bdev_alloc(&ei->bdev)) {
kmem_cache_free(bdev_cachep, ei);
return NULL;
}
return &ei->vfs_inode;
}
static void bdev_free_inode(struct inode *inode)
{
struct block_device *bdev = I_BDEV(inode);
free_percpu(bdev->bd_stats);
kfree(bdev->bd_meta_info);
security_bdev_free(bdev);
if (!bdev_is_partition(bdev)) {
if (bdev->bd_disk && bdev->bd_disk->bdi)
bdi_put(bdev->bd_disk->bdi);
kfree(bdev->bd_disk);
}
if (MAJOR(bdev->bd_dev) == BLOCK_EXT_MAJOR)
blk_free_ext_minor(MINOR(bdev->bd_dev));
kmem_cache_free(bdev_cachep, BDEV_I(inode));
}
static void init_once(void *data)
{
struct bdev_inode *ei = data;
inode_init_once(&ei->vfs_inode);
}
static void bdev_evict_inode(struct inode *inode)
{
truncate_inode_pages_final(&inode->i_data);
invalidate_inode_buffers(inode); /* is it needed here? */
clear_inode(inode);
}
static const struct super_operations bdev_sops = {
.statfs = simple_statfs,
.alloc_inode = bdev_alloc_inode,
.free_inode = bdev_free_inode,
.drop_inode = generic_delete_inode,
.evict_inode = bdev_evict_inode,
};
static int bd_init_fs_context(struct fs_context *fc)
{
struct pseudo_fs_context *ctx = init_pseudo(fc, BDEVFS_MAGIC);
if (!ctx)
return -ENOMEM;
fc->s_iflags |= SB_I_CGROUPWB;
ctx->ops = &bdev_sops;
return 0;
}
static struct file_system_type bd_type = {
.name = "bdev",
.init_fs_context = bd_init_fs_context,
.kill_sb = kill_anon_super,
};
struct super_block *blockdev_superblock __ro_after_init;
static struct vfsmount *blockdev_mnt __ro_after_init;
EXPORT_SYMBOL_GPL(blockdev_superblock);
void __init bdev_cache_init(void)
{
int err;
bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),
0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
SLAB_ACCOUNT|SLAB_PANIC),
init_once);
err = register_filesystem(&bd_type);
if (err)
panic("Cannot register bdev pseudo-fs");
blockdev_mnt = kern_mount(&bd_type);
if (IS_ERR(blockdev_mnt))
panic("Cannot create bdev pseudo-fs");
blockdev_superblock = blockdev_mnt->mnt_sb; /* For writeback */
}
struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
{
struct block_device *bdev;
struct inode *inode;
inode = new_inode(blockdev_superblock);
if (!inode)
return NULL;
inode->i_mode = S_IFBLK;
inode->i_rdev = 0;
inode->i_data.a_ops = &def_blk_aops;
mapping_set_gfp_mask(&inode->i_data, GFP_USER);
bdev = I_BDEV(inode);
mutex_init(&bdev->bd_fsfreeze_mutex);
spin_lock_init(&bdev->bd_size_lock);
mutex_init(&bdev->bd_holder_lock);
atomic_set(&bdev->__bd_flags, partno);
bdev->bd_mapping = &inode->i_data;
bdev->bd_queue = disk->queue;
if (partno && bdev_test_flag(disk->part0, BD_HAS_SUBMIT_BIO))
bdev_set_flag(bdev, BD_HAS_SUBMIT_BIO);
bdev->bd_stats = alloc_percpu(struct disk_stats);
if (!bdev->bd_stats) {
iput(inode);
return NULL;
}
bdev->bd_disk = disk;
return bdev;
}
void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
{
spin_lock(&bdev->bd_size_lock);
i_size_write(BD_INODE(bdev), (loff_t)sectors << SECTOR_SHIFT);
bdev->bd_nr_sectors = sectors;
spin_unlock(&bdev->bd_size_lock);
}
void bdev_add(struct block_device *bdev, dev_t dev)
{
struct inode *inode = BD_INODE(bdev);
if (bdev_stable_writes(bdev))
mapping_set_stable_writes(bdev->bd_mapping);
bdev->bd_dev = dev;
inode->i_rdev = dev;
inode->i_ino = dev;
insert_inode_hash(inode);
}
void bdev_unhash(struct block_device *bdev)
{
remove_inode_hash(BD_INODE(bdev));
}
void bdev_drop(struct block_device *bdev)
{
iput(BD_INODE(bdev));
}
long nr_blockdev_pages(void)
{
struct inode *inode;
long ret = 0;
spin_lock(&blockdev_superblock->s_inode_list_lock);
list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
ret += inode->i_mapping->nrpages;
spin_unlock(&blockdev_superblock->s_inode_list_lock);
return ret;
}
/**
* bd_may_claim - test whether a block device can be claimed
* @bdev: block device of interest
* @holder: holder trying to claim @bdev
* @hops: holder ops
*
* Test whether @bdev can be claimed by @holder.
*
* RETURNS:
* %true if @bdev can be claimed, %false otherwise.
*/
static bool bd_may_claim(struct block_device *bdev, void *holder,
const struct blk_holder_ops *hops)
{
struct block_device *whole = bdev_whole(bdev);
lockdep_assert_held(&bdev_lock);
if (bdev->bd_holder) {
/*
* The same holder can always re-claim.
*/
if (bdev->bd_holder == holder) {
if (WARN_ON_ONCE(bdev->bd_holder_ops != hops))
return false;
return true;
}
return false;
}
/*
* If the whole devices holder is set to bd_may_claim, a partition on
* the device is claimed, but not the whole device.
*/
if (whole != bdev &&
whole->bd_holder && whole->bd_holder != bd_may_claim)
return false;
return true;
}
/**
* bd_prepare_to_claim - claim a block device
* @bdev: block device of interest
* @holder: holder trying to claim @bdev
* @hops: holder ops.
*
* Claim @bdev. This function fails if @bdev is already claimed by another
* holder and waits if another claiming is in progress. return, the caller
* has ownership of bd_claiming and bd_holder[s].
*
* RETURNS:
* 0 if @bdev can be claimed, -EBUSY otherwise.
*/
int bd_prepare_to_claim(struct block_device *bdev, void *holder,
const struct blk_holder_ops *hops)
{
struct block_device *whole = bdev_whole(bdev);
if (WARN_ON_ONCE(!holder))
return -EINVAL;
retry:
mutex_lock(&bdev_lock);
/* if someone else claimed, fail */
if (!bd_may_claim(bdev, holder, hops)) {
mutex_unlock(&bdev_lock);
return -EBUSY;
}
/* if claiming is already in progress, wait for it to finish */
if (whole->bd_claiming) {
wait_queue_head_t *wq = bit_waitqueue(&whole->bd_claiming, 0);
DEFINE_WAIT(wait);
prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
mutex_unlock(&bdev_lock);
schedule();
finish_wait(wq, &wait);
goto retry;
}
/* yay, all mine */
whole->bd_claiming = holder;
mutex_unlock(&bdev_lock);
return 0;
}
EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */
static void bd_clear_claiming(struct block_device *whole, void *holder)
{
lockdep_assert_held(&bdev_lock);
/* tell others that we're done */
BUG_ON(whole->bd_claiming != holder);
whole->bd_claiming = NULL;
wake_up_bit(&whole->bd_claiming, 0);
}
/**
* bd_finish_claiming - finish claiming of a block device
* @bdev: block device of interest
* @holder: holder that has claimed @bdev
* @hops: block device holder operations
*
* Finish exclusive open of a block device. Mark the device as exlusively
* open by the holder and wake up all waiters for exclusive open to finish.
*/
static void bd_finish_claiming(struct block_device *bdev, void *holder,
const struct blk_holder_ops *hops)
{
struct block_device *whole = bdev_whole(bdev);
mutex_lock(&bdev_lock);
BUG_ON(!bd_may_claim(bdev, holder, hops));
/*
* Note that for a whole device bd_holders will be incremented twice,
* and bd_holder will be set to bd_may_claim before being set to holder
*/
whole->bd_holders++;
whole->bd_holder = bd_may_claim;
bdev->bd_holders++;
mutex_lock(&bdev->bd_holder_lock);
bdev->bd_holder = holder;
bdev->bd_holder_ops = hops;
mutex_unlock(&bdev->bd_holder_lock);
bd_clear_claiming(whole, holder);
mutex_unlock(&bdev_lock);
}
/**
* bd_abort_claiming - abort claiming of a block device
* @bdev: block device of interest
* @holder: holder that has claimed @bdev
*
* Abort claiming of a block device when the exclusive open failed. This can be
* also used when exclusive open is not actually desired and we just needed
* to block other exclusive openers for a while.
*/
void bd_abort_claiming(struct block_device *bdev, void *holder)
{
mutex_lock(&bdev_lock);
bd_clear_claiming(bdev_whole(bdev), holder);
mutex_unlock(&bdev_lock);
}
EXPORT_SYMBOL(bd_abort_claiming);
static void bd_end_claim(struct block_device *bdev, void *holder)
{
struct block_device *whole = bdev_whole(bdev);
bool unblock = false;
/*
* Release a claim on the device. The holder fields are protected with
* bdev_lock. open_mutex is used to synchronize disk_holder unlinking.
*/
mutex_lock(&bdev_lock);
WARN_ON_ONCE(bdev->bd_holder != holder);
WARN_ON_ONCE(--bdev->bd_holders < 0);
WARN_ON_ONCE(--whole->bd_holders < 0);
if (!bdev->bd_holders) {
mutex_lock(&bdev->bd_holder_lock);
bdev->bd_holder = NULL;
bdev->bd_holder_ops = NULL;
mutex_unlock(&bdev->bd_holder_lock);
if (bdev_test_flag(bdev, BD_WRITE_HOLDER))
unblock = true;
}
if (!whole->bd_holders)
whole->bd_holder = NULL;
mutex_unlock(&bdev_lock);
/*
* If this was the last claim, remove holder link and unblock evpoll if
* it was a write holder.
*/
if (unblock) {
disk_unblock_events(bdev->bd_disk);
bdev_clear_flag(bdev, BD_WRITE_HOLDER);
}
}
static void blkdev_flush_mapping(struct block_device *bdev)
{
WARN_ON_ONCE(bdev->bd_holders);
sync_blockdev(bdev);
kill_bdev(bdev);
bdev_write_inode(bdev);
}
static void blkdev_put_whole(struct block_device *bdev)
{
if (atomic_dec_and_test(&bdev->bd_openers))
blkdev_flush_mapping(bdev);
if (bdev->bd_disk->fops->release)
bdev->bd_disk->fops->release(bdev->bd_disk);
}
static int blkdev_get_whole(struct block_device *bdev, blk_mode_t mode)
{
struct gendisk *disk = bdev->bd_disk;
int ret;
if (disk->fops->open) {
ret = disk->fops->open(disk, mode);
if (ret) {
/* avoid ghost partitions on a removed medium */
if (ret == -ENOMEDIUM &&
test_bit(GD_NEED_PART_SCAN, &disk->state))
bdev_disk_changed(disk, true);
return ret;
}
}
if (!atomic_read(&bdev->bd_openers))
set_init_blocksize(bdev);
atomic_inc(&bdev->bd_openers);
if (test_bit(GD_NEED_PART_SCAN, &disk->state)) {
/*
* Only return scanning errors if we are called from contexts
* that explicitly want them, e.g. the BLKRRPART ioctl.
*/
ret = bdev_disk_changed(disk, false);
if (ret && (mode & BLK_OPEN_STRICT_SCAN)) {
blkdev_put_whole(bdev);
return ret;
}
}
return 0;
}
static int blkdev_get_part(struct block_device *part, blk_mode_t mode)
{
struct gendisk *disk = part->bd_disk;
int ret;
ret = blkdev_get_whole(bdev_whole(part), mode);
if (ret)
return ret;
ret = -ENXIO;
if (!bdev_nr_sectors(part))
goto out_blkdev_put;
if (!atomic_read(&part->bd_openers)) {
disk->open_partitions++;
set_init_blocksize(part);
}
atomic_inc(&part->bd_openers);
return 0;
out_blkdev_put:
blkdev_put_whole(bdev_whole(part));
return ret;
}
int bdev_permission(dev_t dev, blk_mode_t mode, void *holder)
{
int ret;
ret = devcgroup_check_permission(DEVCG_DEV_BLOCK,
MAJOR(dev), MINOR(dev),
((mode & BLK_OPEN_READ) ? DEVCG_ACC_READ : 0) |
((mode & BLK_OPEN_WRITE) ? DEVCG_ACC_WRITE : 0));
if (ret)
return ret;
/* Blocking writes requires exclusive opener */
if (mode & BLK_OPEN_RESTRICT_WRITES && !holder)
return -EINVAL;
/*
* We're using error pointers to indicate to ->release() when we
* failed to open that block device. Also this doesn't make sense.
*/
if (WARN_ON_ONCE(IS_ERR(holder)))
return -EINVAL;
return 0;
}
static void blkdev_put_part(struct block_device *part)
{
struct block_device *whole = bdev_whole(part);
if (atomic_dec_and_test(&part->bd_openers)) {
blkdev_flush_mapping(part);
whole->bd_disk->open_partitions--;
}
blkdev_put_whole(whole);
}
struct block_device *blkdev_get_no_open(dev_t dev)
{
struct block_device *bdev;
struct inode *inode;
inode = ilookup(blockdev_superblock, dev);
if (!inode && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) {
blk_request_module(dev);
inode = ilookup(blockdev_superblock, dev);
if (inode)
pr_warn_ratelimited(
"block device autoloading is deprecated and will be removed.\n");
}
if (!inode)
return NULL;
/* switch from the inode reference to a device mode one: */
bdev = &BDEV_I(inode)->bdev;
if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
bdev = NULL;
iput(inode);
return bdev;
}
void blkdev_put_no_open(struct block_device *bdev)
{
put_device(&bdev->bd_device);
}
static bool bdev_writes_blocked(struct block_device *bdev)
{
return bdev->bd_writers < 0;
}
static void bdev_block_writes(struct block_device *bdev)
{
bdev->bd_writers--;
}
static void bdev_unblock_writes(struct block_device *bdev)
{
bdev->bd_writers++;
}
static bool bdev_may_open(struct block_device *bdev, blk_mode_t mode)
{
if (bdev_allow_write_mounted)
return true;
/* Writes blocked? */
if (mode & BLK_OPEN_WRITE && bdev_writes_blocked(bdev))
return false;
if (mode & BLK_OPEN_RESTRICT_WRITES && bdev->bd_writers > 0)
return false;
return true;
}
static void bdev_claim_write_access(struct block_device *bdev, blk_mode_t mode)
{
if (bdev_allow_write_mounted)
return;
/* Claim exclusive or shared write access. */
if (mode & BLK_OPEN_RESTRICT_WRITES)
bdev_block_writes(bdev);
else if (mode & BLK_OPEN_WRITE)
bdev->bd_writers++;
}
static inline bool bdev_unclaimed(const struct file *bdev_file)
{
return bdev_file->private_data == BDEV_I(bdev_file->f_mapping->host);
}
static void bdev_yield_write_access(struct file *bdev_file)
{
struct block_device *bdev;
if (bdev_allow_write_mounted)
return;
if (bdev_unclaimed(bdev_file))
return;
bdev = file_bdev(bdev_file);
if (bdev_file->f_mode & FMODE_WRITE_RESTRICTED)
bdev_unblock_writes(bdev);
else if (bdev_file->f_mode & FMODE_WRITE)
bdev->bd_writers--;
}
/**
* bdev_open - open a block device
* @bdev: block device to open
* @mode: open mode (BLK_OPEN_*)
* @holder: exclusive holder identifier
* @hops: holder operations
* @bdev_file: file for the block device
*
* Open the block device. If @holder is not %NULL, the block device is opened
* with exclusive access. Exclusive opens may nest for the same @holder.
*
* CONTEXT:
* Might sleep.
*
* RETURNS:
* zero on success, -errno on failure.
*/
int bdev_open(struct block_device *bdev, blk_mode_t mode, void *holder,
const struct blk_holder_ops *hops, struct file *bdev_file)
{
bool unblock_events = true;
struct gendisk *disk = bdev->bd_disk;
int ret;
if (holder) {
mode |= BLK_OPEN_EXCL;
ret = bd_prepare_to_claim(bdev, holder, hops);
if (ret)
return ret;
} else {
if (WARN_ON_ONCE(mode & BLK_OPEN_EXCL))
return -EIO;
}
disk_block_events(disk);
mutex_lock(&disk->open_mutex);
ret = -ENXIO;
if (!disk_live(disk))
goto abort_claiming;
if (!try_module_get(disk->fops->owner))
goto abort_claiming;
ret = -EBUSY;
if (!bdev_may_open(bdev, mode))
goto put_module;
if (bdev_is_partition(bdev))
ret = blkdev_get_part(bdev, mode);
else
ret = blkdev_get_whole(bdev, mode);
if (ret)
goto put_module;
bdev_claim_write_access(bdev, mode);
if (holder) {
bd_finish_claiming(bdev, holder, hops);
/*
* Block event polling for write claims if requested. Any write
* holder makes the write_holder state stick until all are
* released. This is good enough and tracking individual
* writeable reference is too fragile given the way @mode is
* used in blkdev_get/put().
*/
if ((mode & BLK_OPEN_WRITE) &&
!bdev_test_flag(bdev, BD_WRITE_HOLDER) &&
(disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
bdev_set_flag(bdev, BD_WRITE_HOLDER);
unblock_events = false;
}
}
mutex_unlock(&disk->open_mutex);
if (unblock_events)
disk_unblock_events(disk);
bdev_file->f_flags |= O_LARGEFILE;
bdev_file->f_mode |= FMODE_CAN_ODIRECT;
if (bdev_nowait(bdev))
bdev_file->f_mode |= FMODE_NOWAIT;
if (mode & BLK_OPEN_RESTRICT_WRITES)
bdev_file->f_mode |= FMODE_WRITE_RESTRICTED;
bdev_file->f_mapping = bdev->bd_mapping;
bdev_file->f_wb_err = filemap_sample_wb_err(bdev_file->f_mapping);
bdev_file->private_data = holder;
return 0;
put_module:
module_put(disk->fops->owner);
abort_claiming:
if (holder)
bd_abort_claiming(bdev, holder);
mutex_unlock(&disk->open_mutex);
disk_unblock_events(disk);
return ret;
}
/*
* If BLK_OPEN_WRITE_IOCTL is set then this is a historical quirk
* associated with the floppy driver where it has allowed ioctls if the
* file was opened for writing, but does not allow reads or writes.
* Make sure that this quirk is reflected in @f_flags.
*
* It can also happen if a block device is opened as O_RDWR | O_WRONLY.
*/
static unsigned blk_to_file_flags(blk_mode_t mode)
{
unsigned int flags = 0;
if ((mode & (BLK_OPEN_READ | BLK_OPEN_WRITE)) ==
(BLK_OPEN_READ | BLK_OPEN_WRITE))
flags |= O_RDWR;
else if (mode & BLK_OPEN_WRITE_IOCTL)
flags |= O_RDWR | O_WRONLY;
else if (mode & BLK_OPEN_WRITE)
flags |= O_WRONLY;
else if (mode & BLK_OPEN_READ)
flags |= O_RDONLY; /* homeopathic, because O_RDONLY is 0 */
else
WARN_ON_ONCE(true);
if (mode & BLK_OPEN_NDELAY)
flags |= O_NDELAY;
return flags;
}
struct file *bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
const struct blk_holder_ops *hops)
{
struct file *bdev_file;
struct block_device *bdev;
unsigned int flags;
int ret;
ret = bdev_permission(dev, mode, holder);
if (ret)
return ERR_PTR(ret);
bdev = blkdev_get_no_open(dev);
if (!bdev)
return ERR_PTR(-ENXIO);
flags = blk_to_file_flags(mode);
bdev_file = alloc_file_pseudo_noaccount(BD_INODE(bdev),
blockdev_mnt, "", flags | O_LARGEFILE, &def_blk_fops);
if (IS_ERR(bdev_file)) {
blkdev_put_no_open(bdev);
return bdev_file;
}
ihold(BD_INODE(bdev));
ret = bdev_open(bdev, mode, holder, hops, bdev_file);
if (ret) {
/* We failed to open the block device. Let ->release() know. */
bdev_file->private_data = ERR_PTR(ret);
fput(bdev_file);
return ERR_PTR(ret);
}
return bdev_file;
}
EXPORT_SYMBOL(bdev_file_open_by_dev);
struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
void *holder,
const struct blk_holder_ops *hops)
{
struct file *file;
dev_t dev;
int error;
error = lookup_bdev(path, &dev);
if (error)
return ERR_PTR(error);
file = bdev_file_open_by_dev(dev, mode, holder, hops);
if (!IS_ERR(file) && (mode & BLK_OPEN_WRITE)) {
if (bdev_read_only(file_bdev(file))) {
fput(file);
file = ERR_PTR(-EACCES);
}
}
return file;
}
EXPORT_SYMBOL(bdev_file_open_by_path);
static inline void bd_yield_claim(struct file *bdev_file)
{
struct block_device *bdev = file_bdev(bdev_file);
void *holder = bdev_file->private_data;
lockdep_assert_held(&bdev->bd_disk->open_mutex);
if (WARN_ON_ONCE(IS_ERR_OR_NULL(holder)))
return;
if (!bdev_unclaimed(bdev_file))
bd_end_claim(bdev, holder);
}
void bdev_release(struct file *bdev_file)
{
struct block_device *bdev = file_bdev(bdev_file);
void *holder = bdev_file->private_data;
struct gendisk *disk = bdev->bd_disk;
/* We failed to open that block device. */
if (IS_ERR(holder))
goto put_no_open;
/*
* Sync early if it looks like we're the last one. If someone else
* opens the block device between now and the decrement of bd_openers
* then we did a sync that we didn't need to, but that's not the end
* of the world and we want to avoid long (could be several minute)
* syncs while holding the mutex.
*/
if (atomic_read(&bdev->bd_openers) == 1)
sync_blockdev(bdev);
mutex_lock(&disk->open_mutex);
bdev_yield_write_access(bdev_file);
if (holder)
bd_yield_claim(bdev_file);
/*
* Trigger event checking and tell drivers to flush MEDIA_CHANGE
* event. This is to ensure detection of media removal commanded
* from userland - e.g. eject(1).
*/
disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
if (bdev_is_partition(bdev))
blkdev_put_part(bdev);
else
blkdev_put_whole(bdev);
mutex_unlock(&disk->open_mutex);
module_put(disk->fops->owner);
put_no_open:
blkdev_put_no_open(bdev);
}
/**
* bdev_fput - yield claim to the block device and put the file
* @bdev_file: open block device
*
* Yield claim on the block device and put the file. Ensure that the
* block device can be reclaimed before the file is closed which is a
* deferred operation.
*/
void bdev_fput(struct file *bdev_file)
{
if (WARN_ON_ONCE(bdev_file->f_op != &def_blk_fops))
return;
if (bdev_file->private_data) {
struct block_device *bdev = file_bdev(bdev_file);
struct gendisk *disk = bdev->bd_disk;
mutex_lock(&disk->open_mutex);
bdev_yield_write_access(bdev_file);
bd_yield_claim(bdev_file);
/*
* Tell release we already gave up our hold on the
* device and if write restrictions are available that
* we already gave up write access to the device.
*/
bdev_file->private_data = BDEV_I(bdev_file->f_mapping->host);
mutex_unlock(&disk->open_mutex);
}
fput(bdev_file);
}
EXPORT_SYMBOL(bdev_fput);
/**
* lookup_bdev() - Look up a struct block_device by name.
* @pathname: Name of the block device in the filesystem.
* @dev: Pointer to the block device's dev_t, if found.
*
* Lookup the block device's dev_t at @pathname in the current
* namespace if possible and return it in @dev.
*
* Context: May sleep.
* Return: 0 if succeeded, negative errno otherwise.
*/
int lookup_bdev(const char *pathname, dev_t *dev)
{
struct inode *inode;
struct path path;
int error;
if (!pathname || !*pathname)
return -EINVAL;
error = kern_path(pathname, LOOKUP_FOLLOW, &path);
if (error)
return error;
inode = d_backing_inode(path.dentry);
error = -ENOTBLK;
if (!S_ISBLK(inode->i_mode))
goto out_path_put;
error = -EACCES;
if (!may_open_dev(&path))
goto out_path_put;
*dev = inode->i_rdev;
error = 0;
out_path_put:
path_put(&path);
return error;
}
EXPORT_SYMBOL(lookup_bdev);
/**
* bdev_mark_dead - mark a block device as dead
* @bdev: block device to operate on
* @surprise: indicate a surprise removal
*
* Tell the file system that this devices or media is dead. If @surprise is set
* to %true the device or media is already gone, if not we are preparing for an
* orderly removal.
*
* This calls into the file system, which then typicall syncs out all dirty data
* and writes back inodes and then invalidates any cached data in the inodes on
* the file system. In addition we also invalidate the block device mapping.
*/
void bdev_mark_dead(struct block_device *bdev, bool surprise)
{
mutex_lock(&bdev->bd_holder_lock);
if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead)
bdev->bd_holder_ops->mark_dead(bdev, surprise);
else {
mutex_unlock(&bdev->bd_holder_lock);
sync_blockdev(bdev);
}
invalidate_bdev(bdev);
}
/*
* New drivers should not use this directly. There are some drivers however
* that needs this for historical reasons. For example, the DASD driver has
* historically had a shutdown to offline mode that doesn't actually remove the
* gendisk that otherwise looks a lot like a safe device removal.
*/
EXPORT_SYMBOL_GPL(bdev_mark_dead);
void sync_bdevs(bool wait)
{
struct inode *inode, *old_inode = NULL;
spin_lock(&blockdev_superblock->s_inode_list_lock);
list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
struct address_space *mapping = inode->i_mapping;
struct block_device *bdev;
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
mapping->nrpages == 0) {
spin_unlock(&inode->i_lock);
continue;
}
__iget(inode);
spin_unlock(&inode->i_lock);
spin_unlock(&blockdev_superblock->s_inode_list_lock);
/*
* We hold a reference to 'inode' so it couldn't have been
* removed from s_inodes list while we dropped the
* s_inode_list_lock We cannot iput the inode now as we can
* be holding the last reference and we cannot iput it under
* s_inode_list_lock. So we keep the reference and iput it
* later.
*/
iput(old_inode);
old_inode = inode;
bdev = I_BDEV(inode);
mutex_lock(&bdev->bd_disk->open_mutex);
if (!atomic_read(&bdev->bd_openers)) {
; /* skip */
} else if (wait) {
/*
* We keep the error status of individual mapping so
* that applications can catch the writeback error using
* fsync(2). See filemap_fdatawait_keep_errors() for
* details.
*/
filemap_fdatawait_keep_errors(inode->i_mapping);
} else {
filemap_fdatawrite(inode->i_mapping);
}
mutex_unlock(&bdev->bd_disk->open_mutex);
spin_lock(&blockdev_superblock->s_inode_list_lock);
}
spin_unlock(&blockdev_superblock->s_inode_list_lock);
iput(old_inode);
}
/*
* Handle STATX_{DIOALIGN, WRITE_ATOMIC} for block devices.
*/
void bdev_statx(struct path *path, struct kstat *stat,
u32 request_mask)
{
struct inode *backing_inode;
struct block_device *bdev;
if (!(request_mask & (STATX_DIOALIGN | STATX_WRITE_ATOMIC)))
return;
backing_inode = d_backing_inode(path->dentry);
/*
* Note that backing_inode is the inode of a block device node file,
* not the block device's internal inode. Therefore it is *not* valid
* to use I_BDEV() here; the block device has to be looked up by i_rdev
* instead.
*/
bdev = blkdev_get_no_open(backing_inode->i_rdev);
if (!bdev)
return;
if (request_mask & STATX_DIOALIGN) {
stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
stat->dio_offset_align = bdev_logical_block_size(bdev);
stat->result_mask |= STATX_DIOALIGN;
}
if (request_mask & STATX_WRITE_ATOMIC && bdev_can_atomic_write(bdev)) {
struct request_queue *bd_queue = bdev->bd_queue;
generic_fill_statx_atomic_writes(stat,
queue_atomic_write_unit_min_bytes(bd_queue),
queue_atomic_write_unit_max_bytes(bd_queue));
}
blkdev_put_no_open(bdev);
}
bool disk_live(struct gendisk *disk)
{
return !inode_unhashed(BD_INODE(disk->part0));
}
EXPORT_SYMBOL_GPL(disk_live);
unsigned int block_size(struct block_device *bdev)
{
return 1 << BD_INODE(bdev)->i_blkbits;
}
EXPORT_SYMBOL_GPL(block_size);
static int __init setup_bdev_allow_write_mounted(char *str)
{
if (kstrtobool(str, &bdev_allow_write_mounted))
pr_warn("Invalid option string for bdev_allow_write_mounted:"
" '%s'\n", str);
return 1;
}
__setup("bdev_allow_write_mounted=", setup_bdev_allow_write_mounted);
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