Subject: Re: [PATCH] mingw-multibyte: fix memory acces violation and path length limits.

From: Wataru Noguchi <[email-masked]>
Date: Thu, 03 Oct 2013 07:26:23 +0900

Hi,

At last, I foundfollowing Makefile optimization suppression works fine in my case.

CFLAGS = -g -O2 -fno-inline-small-functions -Wall

Following optimization option cause crash,

-finline-small-functions

// entry.c:237

int checkout_entry(struct cache_entry *ce,
		   const struct checkout *state, char *topath)
{
//------------------------------------------------------------------
// crash!
	static char path[PATH_MAX + 1];
//------------------------------------------------------------------
// works fine. but bad practice.
	static char path[4096 + 1];
//------------------------------------------------------------------
	struct stat st;
	int len = state->base_dir_len;

	if (topath)
		return write_entry(ce, topath, state, 1);

Thanks.

(2013/10/01 22:35), Wataru Noguchi wrote:
> Hi,
>
> Thanks for your patch.
>
> Unfortunately, in my case still crash...
>
> But PATH_MAX length kinds issues interesting.
>
> I'll try investigate a little more.
>
> - PATH_MAX and O2
>
> Thanks.
>
> (2013/10/01 2:00), René Scharfe wrote:
>> Am 29.09.2013 04:56, schrieb Wataru Noguchi:
>>> Hi,
>>>
>>> Thanks for comments.
>>>
>>> My currently working repository is
>>>
>>> https://github.com/wnoguchi/git/tree/hotfix/mingw-multibyte-path-checkout-failure
>>>
>>> I have revert commits to 1f10da3.
>>> I'll try failure step.
>>>
>>> - gcc optimization level is O2.(fail)
>>> - gcc O0, O1 works fine.
>>>
>>>
>>> $ gdb git-clone
>>> GNU gdb 6.8
>>> Copyright (C) 2008 Free Software Foundation, Inc.
>>> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
>>> This is free software: you are free to change and redistribute it.
>>> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
>>> and "show warranty" for details.
>>> This GDB was configured as "i686-pc-mingw32"...
>>> (gdb) r https://github.com/wnoguchi/mingw-checkout-crash.git
>>> Starting program: C:\msysgit\git/git-clone.exe https://github.com/wnoguchi/mingw
>>> -checkout-crash.git
>>> [New thread 800.0xa10]
>>> Error: dll starting at 0x779f0000 not found.
>>> Error: dll starting at 0x75900000 not found.
>>> Error: dll starting at 0x779f0000 not found.
>>> Error: dll starting at 0x778f0000 not found.
>>> [New thread 800.0x92c]
>>> Cloning into 'mingw-checkout-crash'...
>>> Error: dll starting at 0x29f0000 not found.
>>> remote: Counting objects: 8, done.
>>> remote: Compressing objects: 100% (7/7), done.
>>> remote: Total 8 (delta 0), reused 8 (delta 0)
>>> Unpacking objects: 100% (8/8), done.
>>> Checking connectivity... done
>>> [New thread 800.0xea0]
>>>
>>> Program received signal SIGSEGV, Segmentation fault.
>>> 0x004d5200 in git_check_attr (
>>>        path=0xacc6a0 ""..., num=5, check=0x572440) at attr.c:754
>>> 754                     const char *value = check_all_attr[check[i].attr->attr_n
>>> r].value;
>>> (gdb) list
>>> 749             int i;
>>> 750
>>> 751             collect_all_attrs(path);
>>> 752
>>> 753             for (i = 0; i < num; i++) {
>>> 754                     const char *value = check_all_attr[check[i].attr->attr_n
>>> r].value;
>>> 755                     if (value == ATTR__UNKNOWN)
>>> 756                             value = ATTR__UNSET;
>>> 757                     check[i].value = value;
>>> 758             }
>>
>> I get a different crash on Linux if I set PATH_MAX to 260.  The following
>> hackish patch prevents it.  Does it help in your case as well?  If it does
>> then I'll send a nicer (but longer) one.
>>
>> Thanks,
>> René
>>
>>
>> diff --git a/unpack-trees.c b/unpack-trees.c
>> index 1a61e6f..9bd7dcb 100644
>> --- a/unpack-trees.c
>> +++ b/unpack-trees.c
>> @@ -961,7 +961,7 @@ static int clear_ce_flags(struct cache_entry **cache, int nr,
>>                   int select_mask, int clear_mask,
>>                   struct exclude_list *el)
>>   {
>> -    char prefix[PATH_MAX];
>> +    char prefix[4096];
>>       return clear_ce_flags_1(cache, nr,
>>                   prefix, 0,
>>                   select_mask, clear_mask,
>>
>>
>

-- 
================================
   Wataru Noguchi
   [email-masked]
   http://wnoguchi.github.io/
================================

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