linux-kernel - Re: [3.4-rc3] Thread overran stack, or stack corrupted

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Message-ID: <CA+55aFy-uhOgEoEBr-LkOjFQBVh14wwr-20jTrtsg_2EnuNY5g@mail.gmail.com>
Date:	Tue, 17 Apr 2012 13:20:51 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [3.4-rc3] Thread overran stack, or stack corrupted

On Tue, Apr 17, 2012 at 10:21 AM, Dave Jones <davej@...hat.com> wrote:
> My syscall fuzzer started showing up some cases where it we seem to be
> overrunning the stack.  I added a WARN_ON when the stack is really low,
> to see if there's a deep call trace, but it's not really telling me much ..

You seem to have added the WARN_ON() to check_stack_usage() itself.

That's not very useful, because it uses the *current* stack pointer.
Instead, how about just calling "show_trace()" with the actual lowest
stack pointer at that point? That should show you the stack as it was
when it was at its lowest, and that could actually be useful.

IOW, just something like

    show_trace(NULL, NULL, (void *)end_of_stack(p) + lowest_to_date, NULL);

Or something kind of like that. Yes?

                           Linus
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