On Tue 12-02-19 13:24:56, Dan Williams wrote:
> 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.
>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> drivers/dax/super.c | 39 +++++++++++++++++++++++++++++----------
> 1 file changed, 29 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 6e928f37d084..a27395cfcec6 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -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 +115,15 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize)
> return false;
> }
>
> + last_page = ALIGN_DOWN(part_nr_sects_read(bdev->bd_part)
> + - PAGE_SIZE / 512, PAGE_SIZE / 512);
Why not just (i_size_read(bdev->bd_inode) - 1) >> PAGE_SHIFT? Otherwise the
patch looks good to me.
Honza
> + 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 +132,15 @@ 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 +155,20 @@ 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) {
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
