Commit ad428cdb authored by Dan Williams's avatar Dan Williams
Browse files

dax: Check the end of the block-device capacity with dax_direct_access() 



The checks in __bdev_dax_supported() helped mitigate a potential data
corruption bug in the pmem driver's handling of section alignment
padding. Strengthen the checks, including checking the end of the range,
to validate the dev_pagemap, Xarray entries, and sector-to-pfn
translation established for pmem namespaces.

Acked-by: default avatarJan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent fa7d2e63

drivers/dax/super.c

+28 −10
Original line number Diff line number Diff line
@@ -86,12 +86,14 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) 
{

	struct dax_device *dax_dev;

	bool dax_enabled = false;

	pgoff_t pgoff, pgoff_end;

	struct request_queue *q;

	pgoff_t pgoff;

	int err, id;

	pfn_t pfn;

	long len;

	char buf[BDEVNAME_SIZE];

	void *kaddr, *end_kaddr;

	pfn_t pfn, end_pfn;

	sector_t last_page;

	long len, len2;

	int err, id;



	if (blocksize != PAGE_SIZE) {

		pr_debug("%s: error: unsupported blocksize for dax\n",
@@ -113,6 +115,14 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) 
		return false;

	}



	last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * 8;

	err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end);

	if (err) {

		pr_debug("%s: error: unaligned partition for dax\n",

				bdevname(bdev, buf));

		return false;

	}



	dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);

	if (!dax_dev) {

		pr_debug("%s: error: device does not support dax\n",
@@ -121,14 +131,15 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) 
	}



	id = dax_read_lock();

	len = dax_direct_access(dax_dev, pgoff, 1, NULL, &pfn);

	len = dax_direct_access(dax_dev, pgoff, 1, &kaddr, &pfn);

	len2 = dax_direct_access(dax_dev, pgoff_end, 1, &end_kaddr, &end_pfn);

	dax_read_unlock(id);



	put_dax(dax_dev);



	if (len < 1) {

	if (len < 1 || len2 < 1) {

		pr_debug("%s: error: dax access failed (%ld)\n",

				bdevname(bdev, buf), len);

				bdevname(bdev, buf), len < 1 ? len : len2);

		return false;

	}
@@ -143,13 +154,20 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) 
		 */

		WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));

		dax_enabled = true;

	} else if (pfn_t_devmap(pfn)) {

		struct dev_pagemap *pgmap;

	} else if (pfn_t_devmap(pfn) && pfn_t_devmap(end_pfn)) {

		struct dev_pagemap *pgmap, *end_pgmap;



		pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);

		if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX)

		end_pgmap = get_dev_pagemap(pfn_t_to_pfn(end_pfn), NULL);

		if (pgmap && pgmap == end_pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX

				&& pfn_t_to_page(pfn)->pgmap == pgmap

				&& pfn_t_to_page(end_pfn)->pgmap == pgmap

				&& pfn_t_to_pfn(pfn) == PHYS_PFN(__pa(kaddr))

				&& pfn_t_to_pfn(end_pfn) == PHYS_PFN(__pa(end_kaddr)))

			dax_enabled = true;

		put_dev_pagemap(pgmap);

		put_dev_pagemap(end_pgmap);



	}



	if (!dax_enabled) {

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