From: Elliot Berman <quic_eberman@quicinc.com>
To: Sami Tolvanen <samitolvanen@google.com>,
Kees Cook <keescook@chromium.org>
Cc: Elliot Berman <quic_eberman@quicinc.com>,
<linux-kernel@vger.kernel.org>,
Jinlong Mao <jinlmao@codeaurora.org>
Subject: [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace
Date: Wed, 11 Aug 2021 08:59:14 -0700 [thread overview]
Message-ID: <20210811155914.19550-1-quic_eberman@quicinc.com> (raw)
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>
---
kernel/cfi.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/cfi.c b/kernel/cfi.c
index e17a56639766..9594cfd1cf2c 100644
--- a/kernel/cfi.c
+++ b/kernel/cfi.c
@@ -248,9 +248,9 @@ static inline cfi_check_fn find_shadow_check_fn(unsigned long ptr)
{
cfi_check_fn fn;
- rcu_read_lock_sched();
+ rcu_read_lock_sched_notrace();
fn = ptr_to_check_fn(rcu_dereference_sched(cfi_shadow), ptr);
- rcu_read_unlock_sched();
+ rcu_read_unlock_sched_notrace();
return fn;
}
@@ -269,11 +269,11 @@ static inline cfi_check_fn find_module_check_fn(unsigned long ptr)
cfi_check_fn fn = NULL;
struct module *mod;
- rcu_read_lock_sched();
+ rcu_read_lock_sched_notrace();
mod = __module_address(ptr);
if (mod)
fn = mod->cfi_check;
- rcu_read_unlock_sched();
+ rcu_read_unlock_sched_notrace();
return fn;
}
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
next reply other threads:[~2021-08-11 15:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-11 15:59 Elliot Berman [this message]
2021-08-11 16:12 ` [PATCH 1/1] cfi: Use rcu_read_{un}lock_sched_notrace Sami Tolvanen
2021-08-11 20:10 ` Kees Cook
2021-08-11 20:28 ` Konstantin Ryabitsev
2021-08-13 3:33 ` Elliot Berman
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