From: Eric Biggers <ebiggers@xxxxxxxxxx> Michal Suchanek reported [1] that running the pcrypt_aead01 test from LTP [2] in a loop and holding Ctrl-C causes a NULL dereference of alg->cra_users.next in crypto_remove_spawns(), via crypto_del_alg(). The test repeatedly uses CRYPTO_MSG_NEWALG and CRYPTO_MSG_DELALG. The crash occurs when the instance that CRYPTO_MSG_DELALG is trying to unregister isn't a real registered algorithm, but rather is a "test larval", which is a special "algorithm" added to the algorithms list while the real algorithm is still being tested. Larvals don't have initialized cra_users, so that causes the crash. Normally pcrypt_aead01 doesn't trigger this because CRYPTO_MSG_NEWALG waits for the algorithm to be tested; however, CRYPTO_MSG_NEWALG returns early when interrupted. Everything else in the "crypto user configuration" API has this same bug too, i.e. it inappropriately allows operating on larval algorithms (though it doesn't look like the other cases can cause a crash). Fix this by making crypto_alg_match() exclude larval algorithms. [1] https://lkml.kernel.org/r/20190625071624.27039-1-msuchanek@xxxxxxx [2] https://github.com/linux-test-project/ltp/blob/20190517/testcases/kernel/crypto/pcrypt_aead01.c Reported-by: Michal Suchanek <msuchanek@xxxxxxx> Fixes: a38f7907b926 ("crypto: Add userspace configuration API") Cc: <stable@xxxxxxxxxxxxxxx> # v3.2+ Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- crypto/crypto_user_base.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/crypto/crypto_user_base.c b/crypto/crypto_user_base.c index e48da3b75c71d4..a89fcc530092a8 100644 --- a/crypto/crypto_user_base.c +++ b/crypto/crypto_user_base.c @@ -56,6 +56,9 @@ struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact) list_for_each_entry(q, &crypto_alg_list, cra_list) { int match = 0; + if (crypto_is_larval(q)) + continue; + if ((q->cra_flags ^ p->cru_type) & p->cru_mask) continue; -- 2.22.0.410.gd8fdbe21b5-goog
