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Message-ID: <mhng-d888fd65-86fc-4c2d-8a0f-801e9da62701@palmer-ri-x1c9>
Date: Thu, 15 Sep 2022 11:48:22 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: viro@...iv.linux.org.uk, ajones@...tanamicro.com
CC: Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] riscv: fix a nasty sigreturn bug...
> Ping? Does anybody have objections? AFAICS, the bug is still
> there...
Sorry, something's gone off the rails with email and this thread doesn't
show up in my inbox (not even any of the replies). I tried to patch
together this reply manually so hopefully it works.
This is on fixes, thanks -- trying to debug this one would have been a
nightmare.
> On Fri, Sep 24, 2021 at 01:55:27AM +0000, Al Viro wrote:
>> riscv has an equivalent of arm bug fixed by 653d48b22166; if signal
>> gets caught by an interrupt that hits when we have the right value
>> in a0 (-513), *and* another signal gets delivered upon sigreturn()
>> (e.g. included into the blocked mask for the first signal and posted
>> while the handler had been running), the syscall restart logics will
>> see regs->cause equal to EXC_SYSCALL (we are in a syscall, after all)
>> and a0 already restored to its original value (-513, which happens to
>> be -ERESTARTNOINTR) and assume that we need to apply the usual
>> syscall restart logics.
>>
>> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
>> ---
>> diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
>> index c2d5ecbe55264..f8fb85dc94b7a 100644
>> --- a/arch/riscv/kernel/signal.c
>> +++ b/arch/riscv/kernel/signal.c
>> @@ -121,6 +121,8 @@ SYSCALL_DEFINE0(rt_sigreturn)
>> if (restore_altstack(&frame->uc.uc_stack))
>> goto badframe;
>>
>> + regs->cause = -1UL;
>> +
>> return regs->a0;
>>
>> badframe:
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