linux-kernel - [PATCH 3.16 177/217] parisc: Fix kernel crash with reversed copy_from

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Message-ID: <lsq.1461711741.721307016@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:21 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Kees Cook" <keescook@...omium.org>,
	"Helge Deller" <deller@....de>
Subject: [PATCH 3.16 177/217] parisc: Fix kernel crash with reversed
 copy_from_user()

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Helge Deller <deller@....de>

commit ef72f3110d8b19f4c098a0bff7ed7d11945e70c6 upstream.

The kernel module testcase (lib/test_user_copy.c) exhibited a kernel
crash on parisc if the parameters for copy_from_user were reversed
("illegal reversed copy_to_user" testcase).

Fix this potential crash by checking the fault handler if the faulting
address is in the exception table.

Signed-off-by: Helge Deller <deller@....de>
Cc: Kees Cook <keescook@...omium.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/parisc/kernel/traps.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -802,6 +802,9 @@ void notrace handle_interruption(int cod
 
 	    if (fault_space == 0 && !in_atomic())
 	    {
+		/* Clean up and return if in exception table. */
+		if (fixup_exception(regs))
+			return;
 		pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC);
 		parisc_terminate("Kernel Fault", regs, code, fault_address);
 	    }