From: Elliot Berman <quic_eberman@quicinc.com>
To: Kees Cook <keescook@chromium.org>
Cc: Sami Tolvanen <samitolvanen@google.com>,
<linux-kernel@vger.kernel.org>,
Jinlong Mao <jinlmao@codeaurora.org>,
Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
Trilok Soni <tsoni@codeaurora.org>
Subject: Re: [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace
Date: Thu, 12 Aug 2021 20:33:27 -0700 [thread overview]
Message-ID: <2c07a1e7-79b7-b540-e159-a05a4938b6ae@quicinc.com> (raw)
In-Reply-To: <202108111306.527943F39@keescook>
Hi Kees,
On 8/11/2021 1:10 PM, Kees Cook wrote:
> On Wed, Aug 11, 2021 at 08:59:14AM -0700, Elliot Berman wrote:
>> If rcu_read_lock_sched tracing is enabled, the tracing subsystem can
>> perform a jump which needs to be checked by CFI. For example, stm_ftrace
>> source is enabled as a module and hooks into enabled ftrace events. This
>> can cause an recursive loop where find_shadow_check_fn ->
>> rcu_read_lock_sched -> (call to stm_ftrace generates cfi slowpath) ->
>> find_shadow_check_fn -> rcu_read_lock_sched -> ...
>>
>> To avoid the recursion, either the ftrace codes needs to be marked with
>> __no_cfi or CFI should not trace. Use the "_notrace" in CFI to avoid
>> tracing so that CFI can guard ftrace.
>>
>> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
>
> Thanks for this patch! While applying it I noticed that the DKIM
> signature failed. This is actually even visible in the lore archive:
> https://lore.kernel.org/lkml/20210811155914.19550-1-quic_eberman@quicinc.com/raw
> (DKIM_INVALID)
>
> $ b4 am -tls https://lore.kernel.org/lkml/20210811155914.19550-1-quic_eberman@quicinc.com/
> Grabbing thread from lore.kernel.org/lkml/20210811155914.19550-1-quic_eberman%40quicinc.com/t.mbox.gz
> Analyzing 2 messages in the thread
> Checking attestation on all messages, may take a moment...
> ---
> ✗ [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace
> + Reviewed-by: Sami Tolvanen <samitolvanen@google.com> (✓ DKIM/google.com)
> + Signed-off-by: Kees Cook <keescook@chromium.org>
> + Link: https://lore.kernel.org/r/20210811155914.19550-1-quic_eberman@quicinc.com
> ---
> ✗ BADSIG: DKIM/quicinc.com
>
>
>
> Do you know if qualcomm is mangling outbound emails? (i.e. was the
> trailing body suffix added after calculating the DKIM signature?)
It's possible. I will check with our IT department. You may be aware
that Qualcomm was previously using @codeaurora.org mails and this is my
first time using new mail address.
I tried sending a patch to my personal Gmail address and it looked to be
happy with the DKIM signature provided.
Please let me know if I should resend the patch a different way for you
to be able to pull it in.
>
> Thanks!
>
> -Kees
>
prev parent reply other threads:[~2021-08-13 3:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 15:59 [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace Elliot Berman
2021-08-11 16:12 ` Sami Tolvanen
2021-08-11 20:10 ` Kees Cook
2021-08-11 20:28 ` Konstantin Ryabitsev
2021-08-13 3:33 ` Elliot Berman [this message]
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