[PATCH 3.12 41/78] parisc: Fix kernel crash with reversed copy_from_user()

[Jiri Slaby]

From: Helge Deller <deller@xxxxxx>

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

===============

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@xxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 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 1cd1d0c83b6d..cf87b94be7f3 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -806,6 +806,9 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
 
 	    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);
 	    }
-- 
2.8.1