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* [PATCH] block/keyslot-manager: prevent crash when num_slots=1
@ 2020-11-11  2:14 Eric Biggers
  2020-11-11  9:23 ` Christoph Hellwig
  2020-11-11  9:49 ` Satya Tangirala
  0 siblings, 2 replies; 7+ messages in thread
From: Eric Biggers @ 2020-11-11  2:14 UTC (permalink / raw)
  To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Satya Tangirala

From: Eric Biggers <ebiggers@google.com>

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>
---
 block/keyslot-manager.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index 35abcb1ec051d..0a5b2772324ad 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.
+	 */
+	slot_hashtable_size = max(slot_hashtable_size, 2U);
+
 	ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
 	ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
 					     sizeof(ksm->slot_hashtable[0]),

base-commit: f8394f232b1eab649ce2df5c5f15b0e528c92091
-- 
2.29.2


^ permalink raw reply related	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2020-11-16 16:34 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-11  2:14 [PATCH] block/keyslot-manager: prevent crash when num_slots=1 Eric Biggers
2020-11-11  9:23 ` Christoph Hellwig
2020-11-11  9:45   ` Satya Tangirala
2020-11-11 19:25     ` Eric Biggers
2020-11-11 21:50       ` Eric Biggers
2020-11-16 16:34     ` Christoph Hellwig
2020-11-11  9:49 ` Satya Tangirala

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