From: Kees Cook <keescook@chromium.org>
To: Elliot Berman <quic_eberman@quicinc.com>
Cc: Sami Tolvanen <samitolvanen@google.com>,
linux-kernel@vger.kernel.org,
Jinlong Mao <jinlmao@codeaurora.org>,
Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Subject: Re: [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace
Date: Wed, 11 Aug 2021 13:10:36 -0700 [thread overview]
Message-ID: <202108111306.527943F39@keescook> (raw)
In-Reply-To: <20210811155914.19550-1-quic_eberman@quicinc.com>
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?)
Thanks!
-Kees
--
Kees Cook
next prev parent reply other threads:[~2021-08-11 20:10 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 [this message]
2021-08-11 20:28 ` Konstantin Ryabitsev
2021-08-13 3:33 ` Elliot Berman
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