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Message-Id: <1499898783-25732-7-git-send-email-mark.rutland@arm.com>
Date: Wed, 12 Jul 2017 23:33:03 +0100
From: Mark Rutland <mark.rutland@....com>
To: ard.biesheuvel@...aro.org,
kernel-hardening@...ts.openwall.com,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Cc: akashi.takahiro@...aro.org,
catalin.marinas@....com,
dave.martin@....com,
james.morse@....com,
labbott@...oraproject.org,
will.deacon@....com,
keescook@...omium.org,
Mark Rutland <mark.rutland@....com>
Subject: [RFC PATCH 6/6] arm64: add VMAP_STACK and detect out-of-bounds SP
Signed-off-by: Mark Rutland <mark.rutland@....com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/entry.S | 43 +++++++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/traps.c | 21 +++++++++++++++++++++
3 files changed, 65 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b2024db..5cbd961 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1,5 +1,6 @@
config ARM64
def_bool y
+ select HAVE_ARCH_VMAP_STACK
select ACPI_CCA_REQUIRED if ACPI
select ACPI_GENERIC_GSI if ACPI
select ACPI_GTDT if ACPI
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 7c8b164..e0fdb65 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -396,11 +396,54 @@ el1_error_invalid:
inv_entry 1, BAD_ERROR
ENDPROC(el1_error_invalid)
+#ifdef CONFIG_VMAP_STACK
+.macro detect_bad_stack
+ msr sp_el0, x0
+ get_thread_info x0
+ ldr x0, [x0, #TSK_TI_CUR_STK]
+ sub x0, sp, x0
+ and x0, x0, #~(THREAD_SIZE - 1)
+ cbnz x0, __bad_stack
+ mrs x0, sp_el0
+.endm
+
+__bad_stack:
+ /*
+ * Stash the bad SP, and free up another GPR. We no longer care about
+ * EL0 state, since this thread cannot recover.
+ */
+ mov x0, sp
+ msr tpidrro_el0, x0
+ msr tpidr_el0, x1
+
+ /* Move to the emergency stack */
+ adr_this_cpu x0, bad_stack, x1
+ mov x1, #THREAD_START_SP
+ add sp, x0, x1
+
+ /* Restore GPRs and log them to pt_regs */
+ mrs x0, sp_el0
+ mrs x1, tpidr_el0
+ kernel_entry 1
+
+ /* restore the bad SP to pt_regs */
+ mrs x1, tpidrro_el0
+ str x1, [sp, #S_SP]
+
+ /* Time to die */
+ mov x0, sp
+ b handle_bad_stack
+#else
+.macro detect_bad_stack
+.endm
+#endif
+
/*
* EL1 mode handlers.
*/
.align 6
el1_sync:
+ detect_bad_stack
kernel_entry 1
mrs x1, esr_el1 // read the syndrome register
lsr x24, x1, #ESR_ELx_EC_SHIFT // exception class
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 0805b44..84b00e3 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -683,6 +683,27 @@ asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr)
force_sig_info(info.si_signo, &info, current);
}
+#ifdef CONFIG_VMAP_STACK
+DEFINE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], bad_stack) __aligned(16);
+
+asmlinkage void handle_bad_stack(struct pt_regs *regs)
+{
+ unsigned long tsk_stk = (unsigned long)current->stack;
+ unsigned long irq_stk = (unsigned long)per_cpu(irq_stack, smp_processor_id());
+
+ console_verbose();
+ pr_emerg("Stack out-of-bounds!\n"
+ "\tsp: 0x%016lx\n"
+ "\ttsk stack: [0x%016lx..0x%016lx]\n"
+ "\tirq stack: [0x%016lx..0x%016lx]\n",
+ kernel_stack_pointer(regs),
+ tsk_stk, tsk_stk + THREAD_SIZE,
+ irq_stk, irq_stk + THREAD_SIZE);
+ show_regs(regs);
+ panic("stack out-of-bounds");
+}
+#endif
+
void __pte_error(const char *file, int line, unsigned long val)
{
pr_err("%s:%d: bad pte %016lx.\n", file, line, val);
--
1.9.1
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