linux-kernel - Re: Fwd: Re: UML kernel crash of v2.6.36-rcX kernel

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Date:	Mon, 18 Oct 2010 11:08:11 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Toralf Förster <toralf.foerster@....de>
Cc:	Christoph Hellwig <hch@....de>,
	user-mode-linux-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, Richard Weinberger <richard@....at>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: Fwd: Re: UML kernel crash of v2.6.36-rcX kernel

2010/10/18 Toralf Förster <toralf.foerster@....de>:
>
> Christoph Hellwig wrote at 22:18:37
>> I really can't see any relation to the patch.  Can you try the some
>> things in the following order, please:
> ...
>>  (4) re-apply the include/linux/statfs.h changes and see if it still
>>       boots
>
> The first half of step 4 was it (I did not apply the "Definitions for the flag
> in f_flag.") :
>
> diff --git a/include/linux/statfs.h b/include/linux/statfs.h
> index b34cc82..0166d32 100644
> --- a/include/linux/statfs.h
> +++ b/include/linux/statfs.h
> @@ -2,7 +2,6 @@
>  #define _LINUX_STATFS_H
>
>  #include <linux/types.h>
> -
>  #include <asm/statfs.h>
>
>  struct kstatfs {
> @@ -16,7 +15,29 @@ struct kstatfs {
>        __kernel_fsid_t f_fsid;
>        long f_namelen;
>        long f_frsize;
> -   long f_spare[5];
> + long f_flags;
> + long f_spare[4];
>  };

That should only matter for code that accesses the former fifth
element of f_spare[].
fs/compat.c:put_compat_statfs(struct compat_statfs __user *ubuf,
struct kstatfs *kbuf) does that:

            __put_user(0, &ubuf->f_spare[0]) ||
            __put_user(0, &ubuf->f_spare[1]) ||
            __put_user(0, &ubuf->f_spare[2]) ||
            __put_user(0, &ubuf->f_spare[3]) ||
            __put_user(0, &ubuf->f_spare[4]))

Seems struct compat_statfs* may have 4, 5, or 6 elements in the f_spare[] array,
depending on the architecture.

> FWIW the uml kernel boots fine even with that commit however it crashed after
> a special http request : $> wget http://n22_uml/phpsysinfo/

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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