From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: linux-kernel@vger.kernel.org, mhiramat@redhat.com
Subject: Re: + binfmt-introduce-coredump-parameter-structure.patch added to -mm tree
Cc: kosaki.motohiro@jp.fujitsu.com, dhowells@redhat.com,
       hidehiro.kawai.ez@hitachi.com, lethal@linux-sh.org, mingo@elte.hu,
       oleg@redhat.com, roland@redhat.com, vapier@gentoo.org
In-Reply-To: <200911202212.nAKMCF2v012068@imap1.linux-foundation.org>
References: <200911202212.nAKMCF2v012068@imap1.linux-foundation.org>
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Date: Thu, 26 Nov 2009 17:53:24 +0900 (JST)
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Hi Hiramatsu-san,

> 
> The patch titled
>      binfmt: introduce coredump parameter structure
> has been added to the -mm tree.  Its filename is
>      binfmt-introduce-coredump-parameter-structure.patch
> 
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
> 
> See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> out what to do about this
> 
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> 
> ------------------------------------------------------
> Subject: binfmt: introduce coredump parameter structure
> From: Masami Hiramatsu <mhiramat@redhat.com>
> 
> These patches are for fixing coredump mm->flags consistency issue.
> 
> ---
> 1787         if (mm->core_state || !get_dumpable(mm)) {  <- (1)
> 1788                 up_write(&mm->mmap_sem);
> 1789                 put_cred(cred);
> 1790                 goto fail;
> 1791         }
> 1792
> [...]
> 1798         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */ <-(2)
> 1799                 flag = O_EXCL;          /* Stop rewrite attacks */
> 1800                 cred->fsuid = 0;        /* Dump root private */
> 1801         }
> ---
> 
> Since dumpable bits are not protected by lock, there is a chance to change
> these bits between (1) and (2).
> 
> To solve this issue, this patch copies mm->flags to
> coredump_params.mm_flags at the beginning of do_coredump() and uses it
> instead of get_dumpable() while dumping core.  This series also introduce
> coredump parameter structure for simplify bimfmt->core_dump interface.
> 
> 
> 
> This patch:
> 
> Introduce coredump parameter data structure (struct coredump_params) for
> simplifying binfmt->core_dump() arguments.  This also cleanup DUMP_WRITE()
> in elf_core_dump() by style issue.


This patch break ia64 because arch specific ELF_CORE_EXTRA_PHDRS and 
ELF_CORE_WRITE_EXTRA_DATA still use DUMP_WRITE. I expect this patch 
break uml too.


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