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Message-ID: <20201106023546.720372267@goodmis.org>
Date: Thu, 05 Nov 2020 21:32:39 -0500
From: Steven Rostedt (VMware) <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Miroslav Benes <mbenes@...e.cz>,
Petr Mladek <pmladek@...e.com>, Thomas Meyer <thomas@...3r.de>,
Kees Cook <keescook@...omium.org>
Subject: [PATCH 04/11 v3] pstore/ftrace: Add recursion protection to the ftrace callback
From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.
The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.
Link: https://lkml.kernel.org/r/20201028115612.990886844@goodmis.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Meyer <thomas@...3r.de>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
fs/pstore/ftrace.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 5c0450701293..816210fc5d3a 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -28,6 +28,7 @@ static void notrace pstore_ftrace_call(unsigned long ip,
struct ftrace_ops *op,
struct pt_regs *regs)
{
+ int bit;
unsigned long flags;
struct pstore_ftrace_record rec = {};
struct pstore_record record = {
@@ -40,6 +41,10 @@ static void notrace pstore_ftrace_call(unsigned long ip,
if (unlikely(oops_in_progress))
return;
+ bit = ftrace_test_recursion_trylock();
+ if (bit < 0)
+ return;
+
local_irq_save(flags);
rec.ip = ip;
@@ -49,6 +54,7 @@ static void notrace pstore_ftrace_call(unsigned long ip,
psinfo->write(&record);
local_irq_restore(flags);
+ ftrace_test_recursion_unlock(bit);
}
static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
--
2.28.0
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