linux-kernel - [PATCH 1/1] stackleak: Disable function tracing and kprobes for stackleak

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Date:   Tue, 13 Nov 2018 00:08:48 +0300
From:   Alexander Popov <alex.popov@...ux.com>
To:     kernel-hardening@...ts.openwall.com,
        Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>, x86@...nel.org,
        alex.popov@...ux.com, linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] stackleak: Disable function tracing and kprobes for stackleak_erase()

The stackleak_erase() function is called on the trampoline stack at the end
of syscall. This stack is not big enough for ftrace and kprobes operations,
e.g. it can be exhausted if we use kprobe_events for stackleak_erase().

So let's disable function tracing and kprobes for stackleak_erase().

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Alexander Popov <alex.popov@...ux.com>
---
 kernel/stackleak.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/stackleak.c b/kernel/stackleak.c
index e428929..08cb57e 100644
--- a/kernel/stackleak.c
+++ b/kernel/stackleak.c
@@ -11,6 +11,7 @@
  */
 
 #include <linux/stackleak.h>
+#include <linux/kprobes.h>
 
 #ifdef CONFIG_STACKLEAK_RUNTIME_DISABLE
 #include <linux/jump_label.h>
@@ -47,7 +48,7 @@ int stack_erasing_sysctl(struct ctl_table *table, int write,
 #define skip_erasing()	false
 #endif /* CONFIG_STACKLEAK_RUNTIME_DISABLE */
 
-asmlinkage void stackleak_erase(void)
+asmlinkage void notrace stackleak_erase(void)
 {
 	/* It would be nice not to have 'kstack_ptr' and 'boundary' on stack */
 	unsigned long kstack_ptr = current->lowest_stack;
@@ -101,6 +102,7 @@ asmlinkage void stackleak_erase(void)
 	/* Reset the 'lowest_stack' value for the next syscall */
 	current->lowest_stack = current_top_of_stack() - THREAD_SIZE/64;
 }
+NOKPROBE_SYMBOL(stackleak_erase);
 
 void __used stackleak_track_stack(void)
 {
-- 
2.7.4