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dm array: validate array block headers on read

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array_block_check() validates blocknr and csum and nothing else, while
node_check(), next to it, has bounded the structural fields since both
were written. dm_array_cursor_next() takes its loop bound from the
on-disk nr_entries and element_at() is unguarded pointer arithmetic, so
a count larger than the block holds keeps the cursor in one block while
the index grows past it and the read walks off the dm-bufio buffer --
dm_cache_load_mappings() drives it once per cache block at activation.

Check the header against itself: reject a zero value_size, require
max_entries to equal calc_max_entries() for that value_size and block
size, and require nr_entries to fit. Equality rather than an upper bound,
since a count below the real capacity trips BUG_ON() in fill_ablock() and
trim_ablock(). Metadata dm-array writes satisfies all three.

Fixes: 6513c29f44 ("dm persistent data: add transactional array")
Suggested-by: Ming-Hung Tsai <mtsai@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Ming-Hung Tsai <mtsai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Bryam Vargas
2026-07-31 17:54:54 -05:00
committed by Mikulas Patocka
parent 68c5c42567
commit 2965787723
1 changed files with 29 additions and 8 deletions
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37
drivers/md/persistent-data/dm-array.c
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@@ -38,6 +38,14 @@ struct array_block {
*/
#define CSUM_XOR 595846735
/*
* Each array block can hold this many values.
*/
static uint32_t calc_max_entries(size_t value_size, size_t size_of_block)
{
return (size_of_block - sizeof(struct array_block)) / value_size;
}
static void array_block_prepare_for_write(const struct dm_block_validator *v,
struct dm_block *b,
size_t size_of_block)
@@ -55,6 +63,7 @@ static int array_block_check(const struct dm_block_validator *v,
size_t size_of_block)
{
struct array_block *bh_le = dm_block_data(b);
uint32_t nr_entries, max_entries, value_size;
__le32 csum_disk;
if (dm_block_location(b) != le64_to_cpu(bh_le->blocknr)) {
@@ -74,6 +83,26 @@ static int array_block_check(const struct dm_block_validator *v,
return -EILSEQ;
}
nr_entries = le32_to_cpu(bh_le->nr_entries);
max_entries = le32_to_cpu(bh_le->max_entries);
value_size = le32_to_cpu(bh_le->value_size);
if (!value_size) {
DMERR_LIMIT("%s failed: value_size is zero", __func__);
return -EILSEQ;
}
if (max_entries != calc_max_entries(value_size, size_of_block)) {
DMERR_LIMIT("%s failed: max_entries %u invalid for value_size %u",
__func__, max_entries, value_size);
return -EILSEQ;
}
if (nr_entries > max_entries) {
DMERR_LIMIT("%s failed: too many entries", __func__);
return -EILSEQ;
}
return 0;
}
@@ -138,14 +167,6 @@ static void dec_ablock_entries(struct dm_array_info *info, struct array_block *a
on_entries(info, ab, vt->dec);
}
/*
* Each array block can hold this many values.
*/
static uint32_t calc_max_entries(size_t value_size, size_t size_of_block)
{
return (size_of_block - sizeof(struct array_block)) / value_size;
}
/*
* Allocate a new array block. The caller will need to unlock block.
*/