linux-kernel - [PATCH 9/9] samples/kretprobe: correctly check for kthreads

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Message-Id: <20190814104131.20190-10-mark.rutland@arm.com>
Date:   Wed, 14 Aug 2019 11:41:31 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     ak@...ux.intel.com, akpm@...ux-foundation.org,
        bigeasy@...utronix.de, bp@...e.de, catalin.marinas@....com,
        davem@...emloft.net, hch@....de, kan.liang@...el.com,
        mark.rutland@....com, mingo@...nel.org, peterz@...radead.org,
        riel@...riel.com, will@...nel.org
Subject: [PATCH 9/9] samples/kretprobe: correctly check for kthreads

In general, a non-NULL current->mm doesn't imply that current is a
kthread, as kthreads can install an mm via use_mm(), and so it's
preferable to use is_kthread() to determine whether a thread is a
kthread.

For consistency, let's use is_kthread() here.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 samples/kprobes/kretprobe_example.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/kprobes/kretprobe_example.c b/samples/kprobes/kretprobe_example.c
index 186315ca88b3..d6e0bf196f0e 100644
--- a/samples/kprobes/kretprobe_example.c
+++ b/samples/kprobes/kretprobe_example.c
@@ -41,7 +41,7 @@ static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
 {
 	struct my_data *data;
 
-	if (!current->mm)
+	if (is_kthread(current))
 		return 1;	/* Skip kernel threads */
 
 	data = (struct my_data *)ri->data;
-- 
2.11.0