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Subject[PATCH 5.9 092/152] block/keyslot-manager: prevent crash when num_slots=1
Date
From: Eric Biggers <ebiggers@google.com>

[ Upstream commit 47a846536e1bf62626f1c0d8488f3718ce5f8296 ]

If there is only one keyslot, then blk_ksm_init() computes
slot_hashtable_size=1 and log_slot_ht_size=0. This causes
blk_ksm_find_keyslot() to crash later because it uses
hash_ptr(key, log_slot_ht_size) to find the hash bucket containing the
key, and hash_ptr() doesn't support the bits == 0 case.

Fix this by making the hash table always have at least 2 buckets.

Tested by running:

kvm-xfstests -c ext4 -g encrypt -m inlinecrypt \
-o blk-crypto-fallback.num_keyslots=1

Fixes: 1b2628397058 ("block: Keyslot Manager for Inline Encryption")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/keyslot-manager.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index 35abcb1ec051d..86f8195d8039e 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c
@@ -103,6 +103,13 @@ int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
spin_lock_init(&ksm->idle_slots_lock);

slot_hashtable_size = roundup_pow_of_two(num_slots);
+ /*
+ * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
+ * buckets. This only makes a difference when there is only 1 keyslot.
+ */
+ if (slot_hashtable_size < 2)
+ slot_hashtable_size = 2;
+
ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
sizeof(ksm->slot_hashtable[0]),
--
2.27.0


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