Re: + binfmt-introduce-coredump-parameter-structure.patch added to -mm tree

[Masami Hiramatsu <mhiramat@redhat.com>]

Hi Kosaki-san,

KOSAKI Motohiro wrote:
> 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.

$ grep -r DUMP_WRITE arch/*/include
arch/ia64/include/asm/elf.h:            DUMP_WRITE(&phdr, sizeof(phdr));       \
arch/ia64/include/asm/elf.h:                    DUMP_WRITE((void *) gate_phdrs[\

Oops, certainly, that's a problem.
IMHO, we should not do like that, all parameter required by a macro should be
specified explicitly, since it reduces readability so much...
I think we'd better make those macros inline function, check it's return value
for error handling.

What would you think about it?

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com