[Devel] [PATCH hci-8.1] dm-ploop: fix u32 overflow of the delta BAT byte size
Andrey Zhadchenko
andrey.zhadchenko at virtuozzo.com
Mon Oct 26 00:55:52 MSK 2026
Reviewed-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
On 10/9/26 16:23, Alexander Ivanov wrote:
> The byte size of header and BAT, (PLOOP_MAP_OFFSET + m_Size) *
> sizeof(map_index_t), is computed in u32 in several places. It wraps for
> m_Size >= 2^30 - PLOOP_MAP_OFFSET, which a delta with small clusters
> may legally have.
>
> Compute the size in u64 and use ploop_nr_bat_clusters() for the number
> of BAT clusters everywhere.
>
> Reject a header or a resize whose hb_nr exceeds PLOOP_MAX_HB_NR,
> which also keeps DIV_ROUND_UP(hb_nr, 8) and the bitmap size in bits
> from wrapping.
>
> https://virtuozzo.atlassian.net/browse/VSTOR-148171
> Feature: dm-ploop: ploop target driver
> Signed-off-by: Alexander Ivanov <alexander.ivanov at virtuozzo.com>
> ---
> drivers/md/dm-ploop-bat.c | 23 ++++++++++++-----------
> drivers/md/dm-ploop-cmd.c | 19 +++++++++----------
> drivers/md/dm-ploop.h | 6 ++++--
> 3 files changed, 25 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/md/dm-ploop-bat.c b/drivers/md/dm-ploop-bat.c
> index a7849de8aaa6..5ddb8ffdff07 100644
> --- a/drivers/md/dm-ploop-bat.c
> +++ b/drivers/md/dm-ploop-bat.c
> @@ -189,7 +189,6 @@ int ploop_setup_metadata(struct ploop *ploop, struct page *page)
> struct ploop_pvd_header *m_hdr = NULL;
> u32 bat_clusters, offset_clusters;
> struct dm_target *ti = ploop->ti;
> - unsigned long size;
> int ret;
>
> m_hdr = kmap(page);
> @@ -213,8 +212,11 @@ int ploop_setup_metadata(struct ploop *ploop, struct page *page)
> ploop->nr_bat_entries = le32_to_cpu(m_hdr->m_Size);
>
> /* Header and BAT-occupied clusters at start of file */
> - size = (PLOOP_MAP_OFFSET + ploop->nr_bat_entries) * sizeof(map_index_t);
> - bat_clusters = DIV_ROUND_UP(size, CLU_SIZE(ploop));
> + bat_clusters = ploop_nr_bat_clusters(ploop, ploop->nr_bat_entries);
> + if ((u64)bat_clusters + ploop->nr_bat_entries > PLOOP_MAX_HB_NR) {
> + PL_ERR("Too large BAT");
> + goto out;
> + }
>
> /* Clusters from start of file to first data block */
> offset_clusters = SEC_TO_CLU(ploop, le32_to_cpu(m_hdr->m_FirstBlockOffset));
> @@ -242,7 +244,7 @@ static int ploop_delta_check_header(struct ploop *ploop,
> struct rb_root *md_root,
> u32 *delta_nr_be_ret)
> {
> - u32 bytes, delta_nr_be, offset_clusters, bat_clusters;
> + u32 delta_nr_be, offset_clusters, bat_clusters;
> struct md_page *md0 = ploop_md_first_entry(md_root);
> struct ploop_pvd_header *d_hdr;
> int ret = -EPROTO;
> @@ -257,8 +259,7 @@ static int ploop_delta_check_header(struct ploop *ploop,
>
> delta_nr_be = le32_to_cpu(d_hdr->m_Size);
> offset_clusters = SEC_TO_CLU(ploop, le32_to_cpu(d_hdr->m_FirstBlockOffset));
> - bytes = (PLOOP_MAP_OFFSET + delta_nr_be) * sizeof(map_index_t);
> - bat_clusters = DIV_ROUND_UP(bytes, CLU_SIZE(ploop));
> + bat_clusters = ploop_nr_bat_clusters(ploop, delta_nr_be);
>
> if (delta_nr_be > ploop->nr_bat_entries ||
> bat_clusters != offset_clusters)
> @@ -274,13 +275,12 @@ ALLOW_ERROR_INJECTION(ploop_delta_check_header, ERRNO);
> static int ploop_convert_bat_entries(struct ploop *ploop, struct rb_root *md_root,
> u32 nr_be, u32 nr_pages, loff_t file_size)
> {
> - u32 i, end, bytes, bat_clusters, page_id, *bat_entries, max_file_clu;
> + u32 i, end, bat_clusters, page_id, *bat_entries, max_file_clu;
> struct rb_node *node;
> struct md_page *md;
> int ret = 0;
>
> - bytes = (PLOOP_MAP_OFFSET + nr_be) * sizeof(map_index_t);
> - bat_clusters = DIV_ROUND_UP(bytes, CLU_SIZE(ploop));
> + bat_clusters = ploop_nr_bat_clusters(ploop, nr_be);
> max_file_clu = file_size / CLU_SIZE(ploop) - 1;
>
> page_id = 0;
> @@ -311,12 +311,13 @@ int ploop_read_delta_metadata(struct ploop *ploop, struct file *file,
> struct rb_root *md_root, u32 *delta_nr_be_ret)
> {
> struct bio_vec bvec_on_stack, *bvec = &bvec_on_stack;
> - u32 i, size, delta_nr_be, nr_segs;
> + u32 i, delta_nr_be, nr_segs;
> loff_t pos, file_size;
> struct iov_iter iter;
> struct rb_node *node;
> struct md_page *md;
> ssize_t len;
> + u64 size;
> int ret;
>
> ret = -ENOMEM;
> @@ -339,7 +340,7 @@ int ploop_read_delta_metadata(struct ploop *ploop, struct file *file,
> if (ret)
> goto out;
>
> - size = (PLOOP_MAP_OFFSET + delta_nr_be) * sizeof(map_index_t);
> + size = ((u64)delta_nr_be + PLOOP_MAP_OFFSET) * sizeof(map_index_t);
> size = ALIGN(size, PAGE_SIZE); /* file may be open as direct */
> nr_segs = size / PAGE_SIZE;
>
> diff --git a/drivers/md/dm-ploop-cmd.c b/drivers/md/dm-ploop-cmd.c
> index 5fa78e6cff9a..ab17520c2d56 100644
> --- a/drivers/md/dm-ploop-cmd.c
> +++ b/drivers/md/dm-ploop-cmd.c
> @@ -386,7 +386,7 @@ ALLOW_ERROR_INJECTION(ploop_grow_relocate_cluster, ERRNO);
> static int ploop_grow_update_header(struct ploop *ploop,
> struct ploop_cmd *cmd)
> {
> - unsigned int size, first_block_off;
> + unsigned int first_block_off;
> struct ploop_pvd_header *hdr;
> struct ploop_index_wb *piwb;
> u32 nr_be, offset, clus;
> @@ -413,9 +413,7 @@ static int ploop_grow_update_header(struct ploop *ploop,
> }
> piwb = md->piwb;
>
> - size = (PLOOP_MAP_OFFSET + cmd->resize.nr_bat_entries);
> - size *= sizeof(map_index_t);
> - clus = DIV_ROUND_UP(size, CLU_SIZE(ploop));
> + clus = ploop_nr_bat_clusters(ploop, cmd->resize.nr_bat_entries);
> first_block_off = CLU_TO_SEC(ploop, clus);
>
> hdr = kmap_local_page(piwb->bat_page);
> @@ -597,6 +595,11 @@ static int ploop_resize(struct ploop *ploop, sector_t new_sectors)
> }
>
> nr_bat_entries = SEC_TO_CLU(ploop, new_sectors);
> + nr_bat_clusters = ploop_nr_bat_clusters(ploop, nr_bat_entries);
> + if ((u64)nr_bat_clusters + nr_bat_entries > PLOOP_MAX_HB_NR) {
> + DMWARN("resize: too large size is requested");
> + return -EINVAL;
> + }
>
> /* Memory for new md pages */
> ret = ploop_prealloc_md_pages(&cmd.resize.md_pages_root,
> @@ -604,8 +607,6 @@ static int ploop_resize(struct ploop *ploop, sector_t new_sectors)
> if (ret)
> return ret;
>
> - size = (PLOOP_MAP_OFFSET + nr_bat_entries) * sizeof(map_index_t);
> - nr_bat_clusters = DIV_ROUND_UP(size, CLU_SIZE(ploop));
> hb_nr = nr_bat_clusters + nr_bat_entries;
> size = round_up(DIV_ROUND_UP(hb_nr, 8), sizeof(unsigned long));
>
> @@ -1010,11 +1011,9 @@ static int process_flip_upper_deltas(struct ploop *ploop)
> u8 level = ploop_top_level(ploop) - 1;
> struct rb_node *node;
> struct md_page *md;
> - u64 size;
>
> - size = (PLOOP_MAP_OFFSET + READ_ONCE(ploop->nr_bat_entries))
> - * sizeof(map_index_t);
> - bat_clusters = DIV_ROUND_UP(size, CLU_SIZE(ploop));
> + bat_clusters = ploop_nr_bat_clusters(ploop,
> + READ_ONCE(ploop->nr_bat_entries));
> hb_nr = ploop->hb_nr;
>
> /*
> diff --git a/drivers/md/dm-ploop.h b/drivers/md/dm-ploop.h
> index 23662943d56a..5041fc8f1e13 100644
> --- a/drivers/md/dm-ploop.h
> +++ b/drivers/md/dm-ploop.h
> @@ -12,6 +12,8 @@
> #include <linux/bio.h>
>
> #define PLOOP_MAP_OFFSET 16
> +/* Keeps DIV_ROUND_UP(hb_nr, 8) and clu + PLOOP_MAP_OFFSET within u32 */
> +#define PLOOP_MAX_HB_NR round_down(U32_MAX - PLOOP_MAP_OFFSET, 8)
> typedef u32 map_index_t;
> #define BAT_ENTRIES_PER_PAGE (PAGE_SIZE / sizeof(map_index_t))
>
> @@ -410,9 +412,9 @@ static inline unsigned int ploop_nr_pages_in_cluster(struct ploop *ploop)
> static inline unsigned int ploop_nr_bat_clusters(struct ploop *ploop,
> u32 nr_bat_entries)
> {
> - unsigned long size, bat_clusters;
> + u64 size, bat_clusters;
>
> - size = (PLOOP_MAP_OFFSET + nr_bat_entries) * sizeof(map_index_t);
> + size = ((u64)nr_bat_entries + PLOOP_MAP_OFFSET) * sizeof(map_index_t);
> bat_clusters = DIV_ROUND_UP(size, CLU_SIZE(ploop));
>
> return bat_clusters;
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