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* [PATCH] powerpc/64: properly initialise the stackprotector canary on SMP.
@ 2018-10-13  9:45 Christophe Leroy
  2018-10-15  4:01 ` Michael Ellerman
  2018-10-15  9:33 ` [PATCH] " Abdul Haleem
  0 siblings, 2 replies; 3+ messages in thread
From: Christophe Leroy @ 2018-10-13  9:45 UTC (permalink / raw)
  To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, abdhalee
  Cc: linux-kernel, linuxppc-dev

commit 06ec27aea9fc ("powerpc/64: add stack protector support")
doesn't initialise the stack canary on SMP secondary CPU's paca,
leading to the following false positive report from the
stack protector.

smp: Bringing up secondary CPUs ...
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __schedule+0x978/0xa80
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-rc7-next-20181010-autotest-autotest #1
Call Trace:
[c000001fed5b3bf0] [c000000000a0ef3c] dump_stack+0xb0/0xf4 (unreliable)
[c000001fed5b3c30] [c0000000000f9d68] panic+0x140/0x308
[c000001fed5b3cc0] [c0000000000f9844] __stack_chk_fail+0x24/0x30
[c000001fed5b3d20] [c000000000a2c3a8] __schedule+0x978/0xa80
[c000001fed5b3e00] [c000000000a2c9b4] schedule_idle+0x34/0x60
[c000001fed5b3e30] [c00000000013d344] do_idle+0x224/0x3d0
[c000001fed5b3ec0] [c00000000013d6e0] cpu_startup_entry+0x30/0x50
[c000001fed5b3ef0] [c000000000047f34] start_secondary+0x4d4/0x520
[c000001fed5b3f90] [c00000000000b370] start_secondary_prolog+0x10/0x14

This patch properly initialises the stack_canary of the secondary
idle tasks.

Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Fixes: 06ec27aea9fc ("powerpc/64: add stack protector support")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/kernel/smp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 61c1fadbc644..e774d3bf3a03 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -34,6 +34,7 @@
 #include <linux/topology.h>
 #include <linux/profile.h>
 #include <linux/processor.h>
+#include <linux/random.h>
 
 #include <asm/ptrace.h>
 #include <linux/atomic.h>
@@ -810,9 +811,16 @@ static void cpu_idle_thread_init(unsigned int cpu, struct task_struct *idle)
 {
 	struct thread_info *ti = task_thread_info(idle);
 
+#ifdef CONFIG_STACKPROTECTOR
+	idle->stack_canary = get_random_canary();
+#endif
+
 #ifdef CONFIG_PPC64
 	paca_ptrs[cpu]->__current = idle;
 	paca_ptrs[cpu]->kstack = (unsigned long)ti + THREAD_SIZE - STACK_FRAME_OVERHEAD;
+#ifdef CONFIG_STACKPROTECTOR
+	paca_ptrs[cpu]->canary = idle->stack_canary;
+#endif
 #endif
 	ti->cpu = cpu;
 	secondary_ti = current_set[cpu] = ti;
-- 
2.13.3


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: powerpc/64: properly initialise the stackprotector canary on SMP.
  2018-10-13  9:45 [PATCH] powerpc/64: properly initialise the stackprotector canary on SMP Christophe Leroy
@ 2018-10-15  4:01 ` Michael Ellerman
  2018-10-15  9:33 ` [PATCH] " Abdul Haleem
  1 sibling, 0 replies; 3+ messages in thread
From: Michael Ellerman @ 2018-10-15  4:01 UTC (permalink / raw)
  To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras, abdhalee
  Cc: linuxppc-dev, linux-kernel

On Sat, 2018-10-13 at 09:45:12 UTC, Christophe Leroy wrote:
> commit 06ec27aea9fc ("powerpc/64: add stack protector support")
> doesn't initialise the stack canary on SMP secondary CPU's paca,
> leading to the following false positive report from the
> stack protector.
> 
> smp: Bringing up secondary CPUs ...
> Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __schedule+0x978/0xa80
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-rc7-next-20181010-autotest-autotest #1
> Call Trace:
> [c000001fed5b3bf0] [c000000000a0ef3c] dump_stack+0xb0/0xf4 (unreliable)
> [c000001fed5b3c30] [c0000000000f9d68] panic+0x140/0x308
> [c000001fed5b3cc0] [c0000000000f9844] __stack_chk_fail+0x24/0x30
> [c000001fed5b3d20] [c000000000a2c3a8] __schedule+0x978/0xa80
> [c000001fed5b3e00] [c000000000a2c9b4] schedule_idle+0x34/0x60
> [c000001fed5b3e30] [c00000000013d344] do_idle+0x224/0x3d0
> [c000001fed5b3ec0] [c00000000013d6e0] cpu_startup_entry+0x30/0x50
> [c000001fed5b3ef0] [c000000000047f34] start_secondary+0x4d4/0x520
> [c000001fed5b3f90] [c00000000000b370] start_secondary_prolog+0x10/0x14
> 
> This patch properly initialises the stack_canary of the secondary
> idle tasks.
> 
> Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
> Fixes: 06ec27aea9fc ("powerpc/64: add stack protector support")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/7241d26e8175e95290a6549a470c33

cheers

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] powerpc/64: properly initialise the stackprotector canary on SMP.
  2018-10-13  9:45 [PATCH] powerpc/64: properly initialise the stackprotector canary on SMP Christophe Leroy
  2018-10-15  4:01 ` Michael Ellerman
@ 2018-10-15  9:33 ` Abdul Haleem
  1 sibling, 0 replies; 3+ messages in thread
From: Abdul Haleem @ 2018-10-15  9:33 UTC (permalink / raw)
  To: Christophe Leroy
  Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
	linux-kernel, linuxppc-dev

On Sat, 2018-10-13 at 09:45 +0000, Christophe Leroy wrote:
> commit 06ec27aea9fc ("powerpc/64: add stack protector support")
> doesn't initialise the stack canary on SMP secondary CPU's paca,
> leading to the following false positive report from the
> stack protector.
> 
> smp: Bringing up secondary CPUs ...
> Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: __schedule+0x978/0xa80
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.0-rc7-next-20181010-autotest-autotest #1
> Call Trace:
> [c000001fed5b3bf0] [c000000000a0ef3c] dump_stack+0xb0/0xf4 (unreliable)
> [c000001fed5b3c30] [c0000000000f9d68] panic+0x140/0x308
> [c000001fed5b3cc0] [c0000000000f9844] __stack_chk_fail+0x24/0x30
> [c000001fed5b3d20] [c000000000a2c3a8] __schedule+0x978/0xa80
> [c000001fed5b3e00] [c000000000a2c9b4] schedule_idle+0x34/0x60
> [c000001fed5b3e30] [c00000000013d344] do_idle+0x224/0x3d0
> [c000001fed5b3ec0] [c00000000013d6e0] cpu_startup_entry+0x30/0x50
> [c000001fed5b3ef0] [c000000000047f34] start_secondary+0x4d4/0x520
> [c000001fed5b3f90] [c00000000000b370] start_secondary_prolog+0x10/0x14
> 
> This patch properly initialises the stack_canary of the secondary
> idle tasks.
> 
> Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
> Fixes: 06ec27aea9fc ("powerpc/64: add stack protector support")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>  arch/powerpc/kernel/smp.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 61c1fadbc644..e774d3bf3a03 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -34,6 +34,7 @@
>  #include <linux/topology.h>
>  #include <linux/profile.h>
>  #include <linux/processor.h>
> +#include <linux/random.h>
> 
>  #include <asm/ptrace.h>
>  #include <linux/atomic.h>
> @@ -810,9 +811,16 @@ static void cpu_idle_thread_init(unsigned int cpu, struct task_struct *idle)
>  {
>  	struct thread_info *ti = task_thread_info(idle);
> 
> +#ifdef CONFIG_STACKPROTECTOR
> +	idle->stack_canary = get_random_canary();
> +#endif
> +
>  #ifdef CONFIG_PPC64
>  	paca_ptrs[cpu]->__current = idle;
>  	paca_ptrs[cpu]->kstack = (unsigned long)ti + THREAD_SIZE - STACK_FRAME_OVERHEAD;
> +#ifdef CONFIG_STACKPROTECTOR
> +	paca_ptrs[cpu]->canary = idle->stack_canary;
> +#endif
>  #endif
>  	ti->cpu = cpu;
>  	secondary_ti = current_set[cpu] = ti;

Thank you Christophe for the fix, Machine boots fine with above patch.

Reported-and-tested-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>


-- 
Regard's

Abdul Haleem
IBM Linux Technology Centre




^ permalink raw reply	[flat|nested] 3+ messages in thread

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2018-10-15  4:01 ` Michael Ellerman
2018-10-15  9:33 ` [PATCH] " Abdul Haleem

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