Commit bf779220 authored by Li Lingfeng's avatar Li Lingfeng
Browse files

block: Add config option to detect writing to part0 while partitions mounted 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8S3GW


CVE: NA

---------------------------

When a partition of a block device is mounted, opening the entire block
device for write operations may also damage the file system. Identify this
situation.

Signed-off-by: default avatarLi Lingfeng <lilingfeng3@huawei.com>
parent 108aa35d

block/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -249,6 +249,16 @@ config BLK_INLINE_ENCRYPTION_FALLBACK 
	  by falling back to the kernel crypto API when inline

	  encryption hardware is not present.



config BLK_DEV_DETECT_WRITING_PART0

	bool "Detect writing to part0 when partitions mounted"

	default n

	help

	  When partitions of a block device are mounted, writing to part0's

	  buffer cache is likely going to cause filesystem corruption on

	  each partition.

	  As a supplement to BLK_DEV_WRITE_MOUNTED, enabling this

	  to detect the scenario above.



source "block/partitions/Kconfig"



config BLK_MQ_PCI

block/bdev.c

+38 −5
Original line number Diff line number Diff line
@@ -33,9 +33,12 @@ 
#define bdev_write_mounted_opt(opt) (bdev_allow_write_mounted & (1 << BLKDEV_##opt))

/* Should we allow writing to mounted block devices? */

#define BLKDEV_ALLOW_WRITE_MOUNTED	0

/* Should we detect writing to part0 when partitions mounted  */

#define BLKDEV_DETECT_WRITING_PART0	1



static u8 bdev_allow_write_mounted =

	IS_ENABLED(CONFIG_BLK_DEV_WRITE_MOUNTED) << BLKDEV_ALLOW_WRITE_MOUNTED;

	IS_ENABLED(CONFIG_BLK_DEV_WRITE_MOUNTED) << BLKDEV_ALLOW_WRITE_MOUNTED |

	IS_ENABLED(CONFIG_BLK_DEV_DETECT_WRITING_PART0) << BLKDEV_DETECT_WRITING_PART0;



struct bdev_inode {

	struct block_device bdev;
@@ -739,22 +742,52 @@ void blkdev_put_no_open(struct block_device *bdev) 


static bool bdev_writes_blocked(struct block_device *bdev)

{

	return bdev->bd_mounted;

	if (bdev->bd_mounted)

		return true;

	if (bdev_opt(DETECT_WRITING_PART0))

		return bdev_is_partition(bdev) ? bdev_whole(bdev)->bd_mounted :

						 bdev->bd_disk->mount_partitions;



	return false;

}



static void bdev_block_writes(struct block_device *bdev)

{

	bdev->bd_mounted = true;

	if (bdev_is_partition(bdev))

		bdev->bd_disk->mount_partitions++;

}



static void bdev_unblock_writes(struct block_device *bdev)

{

	bdev->bd_mounted = false;

	if (bdev_is_partition(bdev))

		bdev->bd_disk->mount_partitions--;

}



static bool bdev_mount_blocked(struct block_device *bdev)

{

	return bdev->bd_writers > 0;

	if (bdev->bd_writers)

		return true;

	if (bdev_opt(DETECT_WRITING_PART0))

		return bdev_is_partition(bdev) ? bdev_whole(bdev)->bd_writers :

						 bdev->bd_disk->write_open_partitions;



	return false;

}



static void bdev_block_mount(struct block_device *bdev)

{

	bdev->bd_writers++;

	if (bdev_is_partition(bdev))

		bdev->bd_disk->write_open_partitions++;

}



static void bdev_unblock_mount(struct block_device *bdev)

{

	bdev->bd_writers--;

	if (bdev_is_partition(bdev))

		bdev->bd_disk->write_open_partitions--;

}



static bool bdev_may_open(struct block_device *bdev, blk_mode_t mode)
@@ -775,7 +808,7 @@ static void bdev_claim_write_access(struct block_device *bdev, blk_mode_t mode) 
	if (mode & BLK_OPEN_RESTRICT_WRITES)

		bdev_block_writes(bdev);

	else if (mode & BLK_OPEN_WRITE)

		bdev->bd_writers++;

		bdev_block_mount(bdev);

}



static void bdev_yield_write_access(struct block_device *bdev, blk_mode_t mode)
@@ -784,7 +817,7 @@ static void bdev_yield_write_access(struct block_device *bdev, blk_mode_t mode) 
	if (mode & BLK_OPEN_RESTRICT_WRITES)

		bdev_unblock_writes(bdev);

	else if (mode & BLK_OPEN_WRITE)

		bdev->bd_writers--;

		bdev_unblock_mount(bdev);

}



/**

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -162,6 +162,8 @@ struct gendisk { 


	struct mutex open_mutex;	/* open/close mutex */

	unsigned open_partitions;	/* number of open partitions */

	unsigned write_open_partitions;	/* number of write open partitions */

	unsigned mount_partitions;	/* number of mount partitions */



	struct backing_dev_info	*bdi;

	struct kobject queue_kobj;	/* the queue/ directory */