linux-kernel - Re: [PATCH linux-next] powerpc: disable sanitizer in irq_soft_mask

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Message-ID: <6375fd69-d57f-be90-6b17-f183e918dbc8@csgroup.eu>
Date:   Mon, 22 Aug 2022 06:04:01 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Zhouyi Zhou <zhouzhouyi@...il.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "atrajeev@...ux.vnet.ibm.com" <atrajeev@...ux.vnet.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lance@...osl.org" <lance@...osl.org>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "rcu@...r.kernel.org" <rcu@...r.kernel.org>
Subject: Re: [PATCH linux-next] powerpc: disable sanitizer in
 irq_soft_mask_set



Le 21/08/2022 à 03:00, Zhouyi Zhou a écrit :
> In ppc, compiler based sanitizer will generate instrument instructions
> around statement WRITE_ONCE(local_paca->irq_soft_mask, mask):
> 
>     0xc000000000295cb0 <+0>:	addis   r2,r12,774
>     0xc000000000295cb4 <+4>:	addi    r2,r2,16464
>     0xc000000000295cb8 <+8>:	mflr    r0
>     0xc000000000295cbc <+12>:	bl      0xc00000000008bb4c <mcount>
>     0xc000000000295cc0 <+16>:	mflr    r0
>     0xc000000000295cc4 <+20>:	std     r31,-8(r1)
>     0xc000000000295cc8 <+24>:	addi    r3,r13,2354
>     0xc000000000295ccc <+28>:	mr      r31,r13
>     0xc000000000295cd0 <+32>:	std     r0,16(r1)
>     0xc000000000295cd4 <+36>:	stdu    r1,-48(r1)
>     0xc000000000295cd8 <+40>:	bl      0xc000000000609b98 <__asan_store1+8>
>     0xc000000000295cdc <+44>:	nop
>     0xc000000000295ce0 <+48>:	li      r9,1
>     0xc000000000295ce4 <+52>:	stb     r9,2354(r31)
>     0xc000000000295ce8 <+56>:	addi    r1,r1,48
>     0xc000000000295cec <+60>:	ld      r0,16(r1)
>     0xc000000000295cf0 <+64>:	ld      r31,-8(r1)
>     0xc000000000295cf4 <+68>:	mtlr    r0
> 
> If there is a context switch before "stb     r9,2354(r31)", r31 may
> not equal to r13, in such case, irq soft mask will not work.
> 
> This patch disable sanitizer in irq_soft_mask_set.

Well spotted, thanks.

You should add:

Fixes: ef5b570d3700 ("powerpc/irq: Don't open code irq_soft_mask helpers")

By the way, I think the READ_ONCE() likely has the same issue so you 
should fix irq_soft_mask_return() at the same time.

> 
> Signed-off-by: Zhouyi Zhou <zhouzhouyi@...il.com>
> ---
> Dear PPC developers
> 
> I found this bug when trying to do rcutorture tests in ppc VM of
> Open Source Lab of Oregon State University following Paul E. McKenny's guidance.
> 
> console.log report following bug:
> 
> [  346.527467][  T100] BUG: using smp_processor_id() in preemptible [00000000] code: rcu_torture_rea/100^M
> [  346.529416][  T100] caller is rcu_preempt_deferred_qs_irqrestore+0x74/0xed0^M
> [  346.531157][  T100] CPU: 4 PID: 100 Comm: rcu_torture_rea Tainted: G        W          5.19.0-rc5-next-20220708-dirty #253^M
> [  346.533620][  T100] Call Trace:^M
> [  346.534449][  T100] [c0000000094876c0] [c000000000ce2b68] dump_stack_lvl+0xbc/0x108 (unreliable)^M
> [  346.536632][  T100] [c000000009487710] [c000000001712954] check_preemption_disabled+0x154/0x160^M
> [  346.538665][  T100] [c0000000094877a0] [c0000000002ce2d4] rcu_preempt_deferred_qs_irqrestore+0x74/0xed0^M
> [  346.540830][  T100] [c0000000094878b0] [c0000000002cf3c0] __rcu_read_unlock+0x290/0x3b0^M
> [  346.542746][  T100] [c000000009487910] [c0000000002bb330] rcu_torture_read_unlock+0x30/0xb0^M
> [  346.544779][  T100] [c000000009487930] [c0000000002b7ff8] rcutorture_one_extend+0x198/0x810^M
> [  346.546851][  T100] [c000000009487a10] [c0000000002b8bfc] rcu_torture_one_read+0x58c/0xc90^M
> [  346.548844][  T100] [c000000009487ca0] [c0000000002b942c] rcu_torture_reader+0x12c/0x360^M
> [  346.550784][  T100] [c000000009487db0] [c0000000001de978] kthread+0x1e8/0x220^M
> [  346.552555][  T100] [c000000009487e10] [c00000000000cd54] ret_from_kernel_thread+0x5c/0x64^M
> 
> After 12 days debugging, I finally narrow the problem to irq_soft_mask_set.
> 
> I am a beginner, hope I can be of some beneficial to the community ;-)
> 
> Thanks
> Zhouyi
> --
>   arch/powerpc/include/asm/hw_irq.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
> index 26ede09c521d..a5ae8d82cc9d 100644
> --- a/arch/powerpc/include/asm/hw_irq.h
> +++ b/arch/powerpc/include/asm/hw_irq.h
> @@ -121,7 +121,7 @@ static inline notrace unsigned long irq_soft_mask_return(void)
>    * for the critical section and as a clobber because
>    * we changed paca->irq_soft_mask
>    */
> -static inline notrace void irq_soft_mask_set(unsigned long mask)
> +static inline notrace __no_kcsan __no_sanitize_address void irq_soft_mask_set(unsigned long mask)
>   {
>   	/*
>   	 * The irq mask must always include the STD bit if any are set.