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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>, linuxppc-dev@lists.ozlabs.org
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
	Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH kernel v2] powerpc/kuap: Restore AMR after replaying soft interrupts
Date: Thu, 03 Dec 2020 12:08:03 +0530	[thread overview]
Message-ID: <87zh2vjsxg.fsf@linux.ibm.com> (raw)
In-Reply-To: <20201203054724.44838-1-aik@ozlabs.ru>

Alexey Kardashevskiy <aik@ozlabs.ru> writes:

> When interrupted in raw_copy_from_user()/... after user memory access
> is enabled, a nested handler may also access user memory (perf is
> one example) and when it does so, it calls prevent_read_from_user()
> which prevents the upper handler from accessing user memory.
>
> This saves/restores AMR when replaying interrupts.
>
> get_kuap/set_kuap have stubs for disabled KUAP on RADIX but there are
> none for hash-only configs (BOOK3E) so this adds stubs and moves
> AMR_KUAP_BLOCK_xxx.
>
> Found by syzkaller. More likely to break with enabled
> CONFIG_DEBUG_ATOMIC_SLEEP, the call chain is
> timer_interrupt -> ktime_get -> read_seqcount_begin -> local_irq_restore.

Can you test this with https://github.com/kvaneesh/linux/commits/hash-kuap-reworked-2

We do save restore AMR on interrupt entry and exit.

-aneesh


  reply	other threads:[~2020-12-03  6:40 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-03  5:47 [PATCH kernel v2] powerpc/kuap: Restore AMR after replaying soft interrupts Alexey Kardashevskiy
2020-12-03  6:38 ` Aneesh Kumar K.V [this message]
2020-12-03  8:10   ` Alexey Kardashevskiy
2020-12-03  7:41 ` kernel test robot
2020-12-03  7:41   ` kernel test robot
2020-12-03  8:03 ` Christophe Leroy
2020-12-03  8:13   ` Alexey Kardashevskiy
2020-12-04 21:02 ` kernel test robot
2020-12-04 21:02   ` kernel test robot

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