3.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
commit 9cc6d9e5daaa147a9a3e31557efcb331989e77be upstream.
Joachim Eastwood reports that commit fbfb872f5f41 "ARM: 8148/1: flush
TLS and thumbee register state during exec" causes a boot-time crash
on a Cortex-M4 nommu system:
Freeing unused kernel memory: 68K (281e5000 - 281f6000)
Unhandled exception: IPSR = 00000005 LR = fffffff1
CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
task: 29834000 ti: 29832000 task.ti: 29832000
PC is at flush_thread+0x2e/0x40
LR is at flush_thread+0x21/0x40
pc : [<2800954a>] lr : [<2800953d>] psr: 4100000b
sp : 29833d60 ip : 00000000 fp : 00000001
r10: 00003cf8 r9 : 29b1f000 r8 : 00000000
r7 : 29b0bc00 r6 : 29834000 r5 : 29832000 r4 : 29832000
r3 : ffff0ff0 r2 : 29832000 r1 : 00000000 r0 : 282121f0
xPSR: 4100000b
CPU: 0 PID: 1 Comm: swapper Not tainted 3.17.0-rc6-00313-gd2205fa30aa7 #191
[<2800afa5>] (unwind_backtrace) from [<2800a327>] (show_stack+0xb/0xc)
[<2800a327>] (show_stack) from [<2800a963>] (__invalid_entry+0x4b/0x4c)
The problem is that set_tls is attempting to clear the TLS location in
the kernel-user helper page, which isn't set up on V7M.
Fix this by guarding the write to the kuser helper page with
a CONFIG_KUSER_HELPERS ifdef.
Fixes: fbfb872f5f41 ARM: 8148/1: flush TLS and thumbee register state during exec
Reported-by: Joachim Eastwood <manabian@xxxxxxxxx>
Tested-by: Joachim Eastwood <manabian@xxxxxxxxx>
Signed-off-by: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/include/asm/tls.h | 2 ++
1 file changed, 2 insertions(+)
--- a/arch/arm/include/asm/tls.h
+++ b/arch/arm/include/asm/tls.h
@@ -81,6 +81,7 @@ static inline void set_tls(unsigned long
asm("mcr p15, 0, %0, c13, c0, 3"
: : "r" (val));
} else {
+#ifdef CONFIG_KUSER_HELPERS
/*
* User space must never try to access this
* directly. Expect your app to break
@@ -89,6 +90,7 @@ static inline void set_tls(unsigned long
* entry-armv.S for details)
*/
*((unsigned int *)0xffff0ff0) = val;
+#endif
}
}
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