From: Steven Rostedt (VMware) <rostedt@goodmis.org>
Date: Fri, 6 Nov 2020 02:32:39 +0000 (-0500)
Subject: pstore/ftrace: Add recursion protection to the ftrace callback
X-Git-Tag: v5.11-rc1~77^2~29
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=6cdf941871ec9cb1cf03227038a45a73afd8dc9a;p=thirdparty%2Fkernel%2Flinux.git

pstore/ftrace: Add recursion protection to the ftrace callback

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
Link: https://lkml.kernel.org/r/20201106023546.720372267@goodmis.org

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh  Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Meyer <thomas@m3y3r.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---

diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 5c04507012939..816210fc5d3a3 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 = {