On Mon, Nov 06, 2017 at 10:19:51PM -0800, Eric Biggers wrote: > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > On a non-preemptible kernel, if KEYCTL_DH_COMPUTE is called with the > largest permitted inputs (16384 bits), the kernel spends 10+ seconds > doing modular exponentiation in mpi_powm() without rescheduling. If all > threads do it, it locks up the system. Moreover, it can cause > rcu_sched-stall warnings. > > Notwithstanding the insanity of doing this calculation in kernel mode > rather than in userspace, fix it by calling cond_resched() as each bit > from the exponent is processed. It's still noninterruptible, but at > least it's preemptible now. > > Cc: stable@xxxxxxxxxxxxxxx # v4.12+ > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> Patch applied. Thanks. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
