linux-kernel - [PATCH 4.2.y-ckt 49/70] parisc: Fix kernel crash with reversed copy_from

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Message-Id: <1460494375-30070-50-git-send-email-kamal@canonical.com>
Date:	Tue, 12 Apr 2016 13:52:34 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Helge Deller <deller@....de>, Kees Cook <keescook@...omium.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 49/70] parisc: Fix kernel crash with reversed copy_from_user()

4.2.8-ckt8 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

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: Kamal Mostafa <kamal@...onical.com>
---
 arch/parisc/kernel/traps.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index b99b39f..3419668 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -798,6 +798,9 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 
 	    if (fault_space == 0 && !faulthandler_disabled())
 	    {
+		/* 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);
 	    }
-- 
2.7.4