linux-kernel - Re: [PATCH 0/4] alpha: stack fixes

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Message-ID: <Z5uNvYWCwBFuX-W7@minute>
Date: Thu, 30 Jan 2025 15:33:33 +0100
From: Ivan Kokshaysky <ink@...een.parts>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Richard Henderson <richard.henderson@...aro.org>,
	Matt Turner <mattst88@...il.com>, Oleg Nesterov <oleg@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>, Arnd Bergmann <arnd@...db.de>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Magnus Lindholm <linmag7@...il.com>, linux-alpha@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] alpha: stack fixes

On Wed, Jan 29, 2025 at 04:02:26PM +0000, Maciej W. Rozycki wrote:
> On Wed, 29 Jan 2025, Ivan Kokshaysky wrote:
> 
> > Somehow we got away with it until recently, when we ended up with
> > a stack corruption in kernel/smp.c:smp_call_function_single() due to
> > its use of 32-byte aligned local data and the compiler doing clever
> > things allocating it on the stack.
> 
>  Thank you for doing this work.
> 
>  I'll review/verify your changes by hand and push them through GCC and
> glibc regression testing, which should hopefully pick any fallout without 
> having it buried among any intermittent failures, and report back.

Thanks!

>  However, would you please cc <stable@...nel.org> with your submission, v2 
> presumably, so as to have these changes backported?

Sure.

As I need to deal with bpf build failure, v2 is inevitable.

>  The thing is I find it quite a grave bug being fixed here, which has been 
> there for decades and triggering occasionally[1], and it might be the only 
> way for users of certain older systems to get a kernel with the fix 
> already applied.  As you may have been aware non-BWX Alpha support has 
> been removed and while I'm working on bringing it back, it will likely be 
> missing support for specific models such as Jensen there will be no kernel 
> developer to look after.  So getting an LTS kernel might be the only way 
> to get a stable system for some people.

Yes, I know about your work on non-BWX Alpha and highly appreciate it.

> References:
> 
> [1] "System fails to boot when CONFIG_SMP=y", 
>     <https://bugzilla.kernel.org/show_bug.cgi?id=213143>
> 
>   Maciej

Ivan.