20251210-linuxkm-get_drbg-local_bh_disable #9519
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* in get_drbg(), call local_bh_disable() for the crypto_default_rng, and in put_drbg(), call local_bh_enable() if needed. * re-gate migrate_disable() and migrate_enable() so they're called for any SMP kernel >= 5.7, regardless of CONFIG_PREEMPT_COUNT. * in get_drbg_n(), if the caller can't sleep, return immediately if the requested DRBG is busy, to avoid priority inversions and deadlocks.
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retest this please |
sameehj
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Dec 11, 2025
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Looks good overall
The lock values with magic numbers better use define but that maybe be done in a different commit.
ColtonWilley
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Dec 11, 2025
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linuxkm/lkcapi_sha_glue.c:get_drbg(), calllocal_bh_disable()for thecrypto_default_rng, and input_drbg(), calllocal_bh_enable()if needed.migrate_disable()andmigrate_enable()so they're called for any SMP kernel >= 5.7, regardless ofCONFIG_PREEMPT_COUNT.get_drbg_n(), if the caller can't sleep, return immediately if the requested DRBG is busy, to avoid priority inversions and deadlocks.tested with
FORCE_BOOT_LOOP_FOREVER=1 wolfssl-multi-test.sh ... linuxkm-fips-v5-strict-dist-insmod-cust-kernel-2for 101 iterations withdd if=/dev/urandom of=/dev/zero bs=1M count=1200added to the exercise.also tested with
quantum-safe-wolfssl-all-crypto-only-intelasm-fips-dev-linuxkm-next-insmodand'linuxkm-legacy-[56].*-insmod'for portability verification.explanation of the bug fix:
The root cause of the bug was that on non-intelasm modules, the DRBG generator could be interrupted by a softirq that tries to stir entropy into the very same DRBG, resulting in a deadlock as the kthread holding the lock tried to get the lock. With the fixes in this PR, the generator wrapper now always explicitly disables softirqs before locking the DRBG, and the entropy stir-in point of entry fails gracefully if the caller has interrupts disabled and the DRBG can't be locked on the first try.