[ 04/59] ARM: 7384/1: ThumbEE: Disable userspace TEEHBR access for !CONFIG_ARM_THUMBEE

From: Greg KH
Date: Thu Apr 19 2012 - 17:52:26 EST

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


From: Jonathan Austin <Jonathan.Austin@xxxxxxx>

commit 078c04545ba56da21567728a909a496df5ff730d upstream.

Currently when ThumbEE is not enabled (!CONFIG_ARM_THUMBEE) the ThumbEE
register states are not saved/restored at context switch. The default state
of the ThumbEE Ctrl register (TEECR) allows userspace accesses to the
ThumbEE Base Handler register (TEEHBR). This can cause unexpected behaviour
when people use ThumbEE on !CONFIG_ARM_THUMBEE kernels, as well as allowing
covert communication - eg between userspace tasks running inside chroot

This patch sets up TEECR in order to prevent user-space access to TEEHBR
when !CONFIG_ARM_THUMBEE. In this case, tasks are sent SIGILL if they try to
access TEEHBR.

Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Jonathan Austin <jonathan.austin@xxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/arm/mm/proc-v7.S | 12 ++++++++++++
1 file changed, 12 insertions(+)

--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -372,6 +372,18 @@ __v7_setup:
mcr p15, 0, r5, c10, c2, 0 @ write PRRR
mcr p15, 0, r6, c10, c2, 1 @ write NMRR
+ mrc p15, 0, r0, c0, c1, 0 @ read ID_PFR0 for ThumbEE
+ and r0, r0, #(0xf << 12) @ ThumbEE enabled field
+ teq r0, #(1 << 12) @ check if ThumbEE is present
+ bne 1f
+ mov r5, #0
+ mcr p14, 6, r5, c1, c0, 0 @ Initialize TEEHBR to 0
+ mrc p14, 6, r0, c0, c0, 0 @ load TEECR
+ orr r0, r0, #1 @ set the 1st bit in order to
+ mcr p14, 6, r0, c0, c0, 0 @ stop userspace TEEHBR access
adr r5, v7_crval
ldmia r5, {r5, r6}

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