From: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit fbfb872f5f417cea48760c535e0ff027c88b507a upstream.
The TPIDRURO and TPIDRURW registers need to be flushed during exec;
otherwise TLS information is potentially leaked. TPIDRURO in
particular needs careful treatment. Since flush_thread basically
needs the same code used to set the TLS in arm_syscall, pull that into
a common set_tls helper in tls.h and use it in both places.
Similarly, TEEHBR needs to be cleared during exec as well. Clearing
its save slot in thread_info isn't right as there is no guarantee
that a thread switch will occur before the new program runs. Just
setting the register directly is sufficient.
Signed-off-by: Nathan Lynch <nathan_lynch@xxxxxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
arch/arm/include/asm/tls.h | 62 ++++++++++++++++++++++++++++++++++++++++++++++
arch/arm/kernel/process.c | 2 ++
arch/arm/kernel/thumbee.c | 2 +-
arch/arm/kernel/traps.c | 17 +------------
4 files changed, 66 insertions(+), 17 deletions(-)
diff --git a/arch/arm/include/asm/tls.h b/arch/arm/include/asm/tls.h
index 83259b873333..36172adda9d0 100644
--- a/arch/arm/include/asm/tls.h
+++ b/arch/arm/include/asm/tls.h
@@ -1,6 +1,9 @@
#ifndef __ASMARM_TLS_H
#define __ASMARM_TLS_H
+#include <linux/compiler.h>
+#include <asm/thread_info.h>
+
#ifdef __ASSEMBLY__
#include <asm/asm-offsets.h>
.macro switch_tls_none, base, tp, tpuser, tmp1, tmp2
@@ -50,6 +53,47 @@
#endif
#ifndef __ASSEMBLY__
+
+static inline void set_tls(unsigned long val)
+{
+ struct thread_info *thread;
+
+ thread = current_thread_info();
+
+ thread->tp_value[0] = val;
+
+ /*
+ * This code runs with preemption enabled and therefore must
+ * be reentrant with respect to switch_tls.
+ *
+ * We need to ensure ordering between the shadow state and the
+ * hardware state, so that we don't corrupt the hardware state
+ * with a stale shadow state during context switch.
+ *
+ * If we're preempted here, switch_tls will load TPIDRURO from
+ * thread_info upon resuming execution and the following mcr
+ * is merely redundant.
+ */
+ barrier();
+
+ if (!tls_emu) {
+ if (has_tls_reg) {
+ asm("mcr p15, 0, %0, c13, c0, 3"
+ : : "r" (val));
+ } else {
+ /*
+ * User space must never try to access this
+ * directly. Expect your app to break
+ * eventually if you do so. The user helper
+ * at 0xffff0fe0 must be used instead. (see
+ * entry-armv.S for details)
+ */
+ *((unsigned int *)0xffff0ff0) = val;
+ }
+
+ }
+}
+
static inline unsigned long get_tpuser(void)
{
unsigned long reg = 0;
@@ -59,5 +103,23 @@ static inline unsigned long get_tpuser(void)
return reg;
}
+
+static inline void set_tpuser(unsigned long val)
+{
+ /* Since TPIDRURW is fully context-switched (unlike TPIDRURO),
+ * we need not update thread_info.
+ */
+ if (has_tls_reg && !tls_emu) {
+ asm("mcr p15, 0, %0, c13, c0, 2"
+ : : "r" (val));
+ }
+}
+
+static inline void flush_tls(void)
+{
+ set_tls(0);
+ set_tpuser(0);
+}
+
#endif
#endif /* __ASMARM_TLS_H */
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 92f7b15dd221..5f6e650ec9ab 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -334,6 +334,8 @@ void flush_thread(void)
memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
memset(&thread->fpstate, 0, sizeof(union fp_state));
+ flush_tls();
+
thread_notify(THREAD_NOTIFY_FLUSH, thread);
}
diff --git a/arch/arm/kernel/thumbee.c b/arch/arm/kernel/thumbee.c
index 7b8403b76666..80f0d69205e7 100644
--- a/arch/arm/kernel/thumbee.c
+++ b/arch/arm/kernel/thumbee.c
@@ -45,7 +45,7 @@ static int thumbee_notifier(struct notifier_block *self, unsigned long cmd, void
switch (cmd) {
case THREAD_NOTIFY_FLUSH:
- thread->thumbee_state = 0;
+ teehbr_write(0);
break;
case THREAD_NOTIFY_SWITCH:
current_thread_info()->thumbee_state = teehbr_read();
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 1f735aafd5ec..a8dd111ff99a 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -571,7 +571,6 @@ do_cache_op(unsigned long start, unsigned long end, int flags)
#define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
asmlinkage int arm_syscall(int no, struct pt_regs *regs)
{
- struct thread_info *thread = current_thread_info();
siginfo_t info;
if ((no >> 16) != (__ARM_NR_BASE>> 16))
@@ -622,21 +621,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
return regs->ARM_r0;
case NR(set_tls):
- thread->tp_value[0] = regs->ARM_r0;
- if (tls_emu)
- return 0;
- if (has_tls_reg) {
- asm ("mcr p15, 0, %0, c13, c0, 3"
- : : "r" (regs->ARM_r0));
- } else {
- /*
- * User space must never try to access this directly.
- * Expect your app to break eventually if you do so.
- * The user helper at 0xffff0fe0 must be used instead.
- * (see entry-armv.S for details)
- */
- *((unsigned int *)0xffff0ff0) = regs->ARM_r0;
- }
+ set_tls(regs->ARM_r0);
return 0;
#ifdef CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG
--
2.1.1
--
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