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commit f900fde28883602b6c5e1027a6c912b673382aaf upstream. The performance of the crypto fuzz tests has greatly regressed since v5.18. When booting a kernel on an arm64 dev board with all software crypto algorithms and CONFIG_CRYPTO_MANAGER_EXTRA_TESTS enabled, the fuzz tests now take about 200 seconds to run, or about 325 seconds with lockdep enabled, compared to about 5 seconds before. The root cause is that the random number generation has become much slower due to commitd4150779e6("random32: use real rng for non-deterministic randomness"). On my same arm64 dev board, at the time the fuzz tests are run, get_random_u8() is about 345x slower than prandom_u32_state(), or about 469x if lockdep is enabled. Lockdep makes a big difference, but much of the rest comes from the get_random_*() functions taking a *very* slow path when the CRNG is not yet initialized. Since the crypto self-tests run early during boot, even having a hardware RNG driver enabled (CONFIG_CRYPTO_DEV_QCOM_RNG in my case) doesn't prevent this. x86 systems don't have this issue, but they still see a significant regression if lockdep is enabled. Converting the "Fully random bytes" case in generate_random_bytes() to use get_random_bytes() helps significantly, improving the test time to about 27 seconds. But that's still over 5x slower than before. This is all a bit silly, though, since the fuzz tests don't actually need cryptographically secure random numbers. So let's just make them use a non-cryptographically-secure RNG as they did before. The original prandom_u32() is gone now, so let's use prandom_u32_state() instead, with an explicitly managed state, like various other self-tests in the kernel source tree (rbtree_test.c, test_scanf.c, etc.) already do. This also has the benefit that no locking is required anymore, so performance should be even better than the original version that used prandom_u32(). Fixes:d4150779e6("random32: use real rng for non-deterministic randomness") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
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