This is a note to let you know that I've just added the patch titled
ARM: 8198/1: make kuser helpers depend on MMU
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-8198-1-make-kuser-helpers-depend-on-mmu.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 08b964ff3c51b10aaf2e6ba639f40054c09f0f7a Mon Sep 17 00:00:00 2001
From: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
Date: Mon, 10 Nov 2014 23:46:27 +0100
Subject: ARM: 8198/1: make kuser helpers depend on MMU
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From: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
commit 08b964ff3c51b10aaf2e6ba639f40054c09f0f7a upstream.
The kuser helpers page is not set up on non-MMU systems, so it does
not make sense to allow CONFIG_KUSER_HELPERS to be enabled when
CONFIG_MMU=n. Allowing it to be set on !MMU results in an oops in
set_tls (used in execve and the arm_syscall trap handler):
Unhandled exception: IPSR = 00000005 LR = fffffff1
CPU: 0 PID: 1 Comm: swapper Not tainted 3.18.0-rc1-00041-ga30465a #216
task: 8b838000 ti: 8b82a000 task.ti: 8b82a000
PC is at flush_thread+0x32/0x40
LR is at flush_thread+0x21/0x40
pc : [<8f00157a>] lr : [<8f001569>] psr: 4100000b
sp : 8b82be20 ip : 00000000 fp : 8b83c000
r10: 00000001 r9 : 88018c84 r8 : 8bb85000
r7 : 8b838000 r6 : 00000000 r5 : 8bb77400 r4 : 8b82a000
r3 : ffff0ff0 r2 : 8b82a000 r1 : 00000000 r0 : 88020354
xPSR: 4100000b
CPU: 0 PID: 1 Comm: swapper Not tainted 3.18.0-rc1-00041-ga30465a #216
[<8f002bc1>] (unwind_backtrace) from [<8f002033>] (show_stack+0xb/0xc)
[<8f002033>] (show_stack) from [<8f00265b>] (__invalid_entry+0x4b/0x4c)
As best I can tell this issue existed for the set_tls ARM syscall
before commit fbfb872f5f41 "ARM: 8148/1: flush TLS and thumbee
register state during exec" consolidated the TLS manipulation code
into the set_tls helper function, but now that we're using it to flush
register state during execve, !MMU users encounter the oops at the
first exec.
Prevent CONFIG_MMU=n configurations from enabling
CONFIG_KUSER_HELPERS.
Fixes: fbfb872f5f41 (ARM: 8148/1: flush TLS and thumbee register state during exec)
Signed-off-by: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
Reported-by: Stefan Agner <stefan@xxxxxxxx>
Acked-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/Kconfig | 1 +
1 file changed, 1 insertion(+)
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -798,6 +798,7 @@ config NEED_KUSER_HELPERS
config KUSER_HELPERS
bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
+ depends on MMU
default y
help
Warning: disabling this option may break user programs.
Patches currently in stable-queue which might be from nathan_lynch@xxxxxxxxxx are
queue-3.17/arm-8198-1-make-kuser-helpers-depend-on-mmu.patch
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