linux-kernel - Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put

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Date:   Sun, 6 Oct 2019 17:23:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to
 unsafe_put_user()

On Sun, Oct 06, 2019 at 04:06:16PM -0700, Linus Torvalds wrote:
> On Sun, Oct 6, 2019 at 3:20 PM Guenter Roeck <linux@...ck-us.net> wrote:
> >
> > this patch causes all my sparc64 emulations to stall during boot. It causes
> > all alpha emulations to crash with [1a] and [1b] when booting from a virtual
> > disk, and one of the xtensa emulations to crash with [2].
> 
> Ho humm. I've run variations of that patch over a few years on x86,
> but obviously not on alpha/sparc.
> 
> At least I should still be able to read alpha assembly, even after all
> these years. Would you mind sending me the result of
> 
>     make fs/readdir.s
> 
> on alpha with the broken config? I'd hope that the sparc issue is the same.
> 
> Actually, could you also do
> 
>     make fs/readdir.o
> 
> and then send me the "objdump --disassemble" of that? That way I get
> the instruction offsets without having to count by hand.
> 

Both attached for alpha.

> > Unable to handle kernel paging request at virtual address 0000000000000004
> > rcS(47): Oops -1
> > pc = [<0000000000000004>]  ra = [<fffffc00004512e4>]  ps = 0000    Not tainted
> > pc is at 0x4
> 
> That is _funky_. I'm not seeing how it could possibly jump to 0x4, but
> it clearly does.
> 
> That said, are you sure it's _that_ commit? Because this pattern:
> 
Bisect on sparc pointed to this commit, and re-running the tests with
the commit reverted passed for all architectures. I didn't check any
further.

Please let me know if you need anything else at this point.

Thanks,
Guenter

View attachment "readdir.s" of type "text/plain" (65439 bytes)

View attachment "readdir.s.objdump" of type "text/plain" (32016 bytes)