linux-kernel - [PATCH 2/3] drivers/tty: Explicitly pass current to show

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Message-Id: <1474902979-18436-3-git-send-email-mark.rutland@arm.com>
Date:   Mon, 26 Sep 2016 16:16:18 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH 2/3] drivers/tty: Explicitly pass current to show_stack

As noted in commit:

  81539169f283329f ("x86/dumpstack: Remove NULL task pointer convention")

... having a NULL task parameter imply current leads to subtle bugs in stack
walking code (so far seen on both 86 and arm64), makes callsites harder to
read, and is unnecessary as all callers have access to current.

As a step towards removing the problematic NULL-implies-current idiom entirely,
have the sysrq code explicitly pass current to show_stack.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: linux-kernel@...r.kernel.org
---
 drivers/tty/sysrq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 52bbd27..5b1e0ed 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -224,7 +224,7 @@ static void showacpu(void *dummy)
 
 	spin_lock_irqsave(&show_lock, flags);
 	pr_info("CPU%d:\n", smp_processor_id());
-	show_stack(NULL, NULL);
+	show_stack(current, NULL);
 	spin_unlock_irqrestore(&show_lock, flags);
 }
 
-- 
2.7.4