linux-kernel - [PATCH] ia64: Pin controlling tty for unaligned fault message

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Message-Id: <1413486653-26010-1-git-send-email-peter@hurleysoftware.com>
Date:	Thu, 16 Oct 2014 15:10:53 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-ia64@...r.kernel.org>, linux-kernel@...r.kernel.org,
	Peter Hurley <peter@...leysoftware.com>
Subject: [PATCH] ia64: Pin controlling tty for unaligned fault message

Prevent destruction of the controlling tty before tty_write_message()
can determine if the tty is safe to use.

Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
 arch/ia64/kernel/unaligned.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/unaligned.c b/arch/ia64/kernel/unaligned.c
index 622772b..e7ae608 100644
--- a/arch/ia64/kernel/unaligned.c
+++ b/arch/ia64/kernel/unaligned.c
@@ -1336,8 +1336,11 @@ ia64_handle_unaligned (unsigned long ifa, struct pt_regs *regs)
 			 * Don't call tty_write_message() if we're in the kernel; we might
 			 * be holding locks...
 			 */
-			if (user_mode(regs))
-				tty_write_message(current->signal->tty, buf);
+			if (user_mode(regs)) {
+				struct tty_struct *tty = get_current_tty();
+				tty_write_message(tty, buf);
+				tty_kref_put(tty);
+			}
 			buf[len-1] = '\0';	/* drop '\r' */
 			/* watch for command names containing %s */
 			printk(KERN_WARNING "%s", buf);
-- 
2.1.1

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