[PATCH linux-next] powerpc: disable sanitizer in irq_soft_mask_set
Zhouyi Zhou
zhouzhouyi at gmail.com
Tue Aug 23 11:43:04 AEST 2022
On Mon, Aug 22, 2022 at 2:04 PM Christophe Leroy
<christophe.leroy at csgroup.eu> wrote:
>
>
>
> 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.
Thank Christophe for reviewing my patch and your guidance!
>
> You should add:
>
> Fixes: ef5b570d3700 ("powerpc/irq: Don't open code irq_soft_mask helpers")
OK, I will do it!
>
> 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.
Yes, after disassembling irq_soft_mask_return, she has the same issue
as irq_soft_mask_set.
In addition, I read hw_irq.h by naked eye to search for removed inline
assembly one by one,
I found another place that we could possible enhance (Thank Paul E.
McKenny for teaching me use git blame ;-)):
077fc62b2b66a("powerpc/irq: remove inline assembly in hard_irq_disable macro")
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -282,9 +282,7 @@ static inline bool pmi_irq_pending(void)
flags = irq_soft_mask_set_return(IRQS_ALL_DISABLED); \
local_paca->irq_happened |= PACA_IRQ_HARD_DIS; \
if (!arch_irqs_disabled_flags(flags)) { \
- asm ("stdx %%r1, 0, %1 ;" \
- : "=m" (local_paca->saved_r1) \
- : "b" (&local_paca->saved_r1)); \
+ WRITE_ONCE(local_paca->saved_r1, current_stack_pointer);\
trace_hardirqs_off(); \
} \
} while(0)
I wrap the macro hard_irq_disable into a test function and disassemble
it, she has the above issue too:
(gdb) disassemble test002
Dump of assembler code for function test002:
0xc000000000295db0 <+0>: addis r2,r12,774
0xc000000000295db4 <+4>: addi r2,r2,16464
0xc000000000295db8 <+8>: mflr r0
0xc000000000295dbc <+12>: bl 0xc00000000008bacc <mcount>
0xc000000000295dc0 <+16>: mflr r0
0xc000000000295dc4 <+20>: std r30,-16(r1)
0xc000000000295dc8 <+24>: std r31,-8(r1)
0xc000000000295dcc <+28>: li r9,2
0xc000000000295dd0 <+32>: std r0,16(r1)
0xc000000000295dd4 <+36>: stdu r1,-48(r1)
0xc000000000295dd8 <+40>: mtmsrd r9,1
0xc000000000295ddc <+44>: addi r3,r13,2354
0xc000000000295de0 <+48>: mr r31,r13
0xc000000000295de4 <+52>: bl 0xc000000000609838 <__asan_load1+8>
0xc000000000295de8 <+56>: nop
0xc000000000295dec <+60>: li r3,3
0xc000000000295df0 <+64>: lbz r30,2354(r31)
0xc000000000295df4 <+68>: bl 0xc00000000028de90 <irq_soft_mask_set>
0xc000000000295df8 <+72>: mr r31,r13
0xc000000000295dfc <+76>: addi r3,r13,2355
0xc000000000295e00 <+80>: bl 0xc000000000609838 <__asan_load1+8>
0xc000000000295e04 <+84>: nop
0xc000000000295e08 <+88>: lbz r9,2355(r31)
0xc000000000295e0c <+92>: andi. r10,r30,1
0xc000000000295e10 <+96>: ori r9,r9,1
0xc000000000295e14 <+100>: stb r9,2355(r31)
0xc000000000295e18 <+104>: bne 0xc000000000295e30 <test002+128>
0xc000000000295e1c <+108>: mr r30,r1
0xc000000000295e20 <+112>: addi r3,r31,2328
0xc000000000295e24 <+116>: bl 0xc000000000609dd8 <__asan_store8+8>
0xc000000000295e28 <+120>: nop
0xc000000000295e2c <+124>: std r30,2328(r31)
0xc000000000295e30 <+128>: addi r1,r1,48
0xc000000000295e34 <+132>: ld r0,16(r1)
0xc000000000295e38 <+136>: ld r30,-16(r1)
0xc000000000295e3c <+140>: ld r31,-8(r1)
0xc000000000295e40 <+144>: mtlr r0
0xc000000000295e44 <+148>: blr
Could we rewrite this macro into a static inline function as
irq_soft_mask_set does, and disable sanitizer for it?
Thanks again
Cheers
Zhouyi
>
> >
> > Signed-off-by: Zhouyi Zhou <zhouzhouyi at gmail.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.
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