Re: [RESEND][mmotm][PATCH v2, 0/5] elf coredump: Add extended numbering support

[Masami Hiramatsu <mhiramat@redhat.com>]

Andrew Morton wrote:
> On Thu, 7 Jan 2010 16:29:28 -0800
> Andrew Morton <akpm@linux-foundation.org> wrote:
> 
>> On Mon, 04 Jan 2010 10:06:07 +0900 (JST)
>> Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com> wrote:
>>
>>> The current ELF dumper can produce broken corefiles if program headers
>>> exceed 65535. In particular, the program in 64-bit environment often
>>> demands more than 65535 mmaps. If you google max_map_count, then you
>>> can find many users facing this problem.
>>>
>>> Solaris has already dealt with this issue, and other OSes have also
>>> adopted the same method as in Solaris. Currently, Sun's document and
>>> AMD 64 ABI include the description for the extension, where they call
>>> the extension Extended Numbering. See Reference for further information.
>>>
>>> I believe that linux kernel should adopt the same way as they did, so
>>> I've written this patch.
>>>
>>> I am also preparing for patches of GDB and binutils.
>>
>> That's a beautifully presented patchset.  Thanks for doing all that
>> work - it helps.
>>
>> UML maintenance appears to have ceased in recent times, so if we wish
>> to have these changes runtime tested (we should) then I think it would
>> be best if you could find someone to do that please.
>>
>> And no akpm code-review would be complete without: dump_seek() is
>> waaaay to large to be inlined.  Is there some common .c file to where
>> we could move it?
>>
> 
> Also, these patches made a bit of a mess of
> mm-pass-mm-flags-as-a-coredump-parameter-for-consistency.patch.
> 
> I consider
> mm-pass-mm-flags-as-a-coredump-parameter-for-consistency.patch to be
> less important (although older) than this patch series so I've fixed up
> mm-pass-mm-flags-as-a-coredump-parameter-for-consistency.patch and have
> staged it after your patch series.  If this causes problems then I'll
> drop mm-pass-mm-flags-as-a-coredump-parameter-for-consistency.patch,
> sorry.

Sure, that's fine to me too.
It seems that those patches are not conflict each other directly.

Thank you for modifying my patch.
And I found just two misses.

> From: Masami Hiramatsu <mhiramat@redhat.com>
> 
> Pass mm->flags as a coredump parameter for consistency.
> 
>  ---
> 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 copy is also passed to binfmt->core_dump, since elf*_core_dump() uses
> dump_filter bits in mm->flags.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> Acked-by: Roland McGrath <roland@redhat.com>
> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  fs/binfmt_elf.c         |   12 ++----------
>  fs/binfmt_elf_fdpic.c   |   12 ++----------
>  fs/exec.c               |   20 ++++++++++++++++----
>  include/linux/binfmts.h |    1 +
>  4 files changed, 21 insertions(+), 24 deletions(-)
> 
> diff -puN fs/binfmt_elf.c~mm-pass-mm-flags-as-a-coredump-parameter-for-consistency fs/binfmt_elf.c
> --- a/fs/binfmt_elf.c~mm-pass-mm-flags-as-a-coredump-parameter-for-consistency
> +++ a/fs/binfmt_elf.c
> @@ -1905,7 +1905,6 @@ static int elf_core_dump(struct coredump
>  	struct vm_area_struct *vma, *gate_vma;
>  	struct elfhdr *elf = NULL;
>  	loff_t offset = 0, dataoff, foffset;
> -	unsigned long mm_flags;
>  	struct elf_note_info info;
>  	struct elf_phdr *phdr4note = NULL;
>  	struct elf_shdr *shdr4extnum = NULL;
> @@ -1980,13 +1979,6 @@ static int elf_core_dump(struct coredump
>  
>  	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
>  
> -	/*
> -	 * We must use the same mm->flags while dumping core to avoid
> -	 * inconsistency between the program headers and bodies, otherwise an
> -	 * unusable core file can be generated.
> -	 */
> -	mm_flags = current->mm->flags;
> -
>  	offset += elf_core_vma_data_size(gate_vma, mm_flags);
						   ^^^^^^^^ cprm->mm_flags

>  	offset += elf_core_extra_data_size();
>  	e_shoff = offset;
> @@ -2018,7 +2010,7 @@ static int elf_core_dump(struct coredump
>  		phdr.p_offset = offset;
>  		phdr.p_vaddr = vma->vm_start;
>  		phdr.p_paddr = 0;
> -		phdr.p_filesz = vma_dump_size(vma, mm_flags);
> +		phdr.p_filesz = vma_dump_size(vma, cprm->mm_flags);
>  		phdr.p_memsz = vma->vm_end - vma->vm_start;
>  		offset += phdr.p_filesz;
>  		phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
> @@ -2053,7 +2045,7 @@ static int elf_core_dump(struct coredump
>  		unsigned long addr;
>  		unsigned long end;
>  
> -		end = vma->vm_start + vma_dump_size(vma, mm_flags);
> +		end = vma->vm_start + vma_dump_size(vma, cprm->mm_flags);
>  
>  		for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
>  			struct page *page;
> diff -puN fs/binfmt_elf_fdpic.c~mm-pass-mm-flags-as-a-coredump-parameter-for-consistency fs/binfmt_elf_fdpic.c
> --- a/fs/binfmt_elf_fdpic.c~mm-pass-mm-flags-as-a-coredump-parameter-for-consistency
> +++ a/fs/binfmt_elf_fdpic.c
> @@ -1623,7 +1623,6 @@ static int elf_fdpic_core_dump(struct co
>  #endif
>  	int thread_status_size = 0;
>  	elf_addr_t *auxv;
> -	unsigned long mm_flags;
>  	struct elf_phdr *phdr4note = NULL;
>  	struct elf_shdr *shdr4extnum = NULL;
>  	Elf_Half e_phnum;
> @@ -1766,13 +1765,6 @@ static int elf_fdpic_core_dump(struct co
>  	/* Page-align dumped data */
>  	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
>  
> -	/*
> -	 * We must use the same mm->flags while dumping core to avoid
> -	 * inconsistency between the program headers and bodies, otherwise an
> -	 * unusable core file can be generated.
> -	 */
> -	mm_flags = current->mm->flags;
> -
>  	offset += elf_core_vma_data_size(mm_flags);
                                         ^^^^^^^^ cprm->mm_flags

Thanks!

-- 
Masami Hiramatsu

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

e-mail: mhiramat@redhat.com

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