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dm-integrity: fix infinite loop on discard with large tag size

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When integrity_metadata handles a discard, it fills a buffer with
DISCARD_FILLER and writes it over the tags, max_blocks blocks at a
time. If the kmalloc fails, the buffer is the on-stack array
checksums_onstack and max_size is set to HASH_MAX_DIGESTSIZE. So if the
tag size is larger than HASH_MAX_DIGESTSIZE, max_blocks is zero, bi_size
is never decremented and the loop never terminates.

Fix this by using sizeof(checksums_onstack) as max_size. The array has
MAX_TAG_SIZE bytes since commit b93b6643e9 ("dm integrity: fix a
crash with unusually large tag size"), so max_blocks is at least 1.

Fixes: 84597a44a9 ("dm integrity: add optional discard support")
Cc: stable@vger.kernel.org
Reviewed-by: Jose Fernandez (Anthropic) <jose.fernandez@linux.dev>
Signed-off-by: Ben Cressey <ben@cressey.dev>
Assisted-by: Claude:unspecified
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This commit is contained in:
Ben Cressey 2026-08-20 21:44:58 +00:00 committed by Mikulas Patocka
parent 59e6f919d7
commit 18d80c77b4
1 changed files with 1 additions and 1 deletions
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2
drivers/md/dm-integrity.c
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@ -1979,7 +1979,7 @@ static void integrity_metadata(struct work_struct *w)
if (unlikely(dio->op == REQ_OP_DISCARD)) {
unsigned int bi_size = dio->bio_details.bi_iter.bi_size;
unsigned int max_size = likely(checksums != checksums_onstack) ? PAGE_SIZE : HASH_MAX_DIGESTSIZE;
unsigned int max_size = likely(checksums != checksums_onstack) ? PAGE_SIZE : sizeof(checksums_onstack);
unsigned int max_blocks = (max_size - extra_space) / ic->tag_size;
sector_t sector = dio->range.logical_sector;