GNU bug report logs - #55023
Issue with CP empty folder after y2038 on 32-bits Kernel

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From: Pádraig Brady <P <at> draigBrady.com>
To: Adhemerval Zanella <adhemerval.zanella <at> linaro.org>, Arnaud Panaïotis <arnaud.panaiotis <at> gmx.fr>, 55023 <at> debbugs.gnu.org
Subject: bug#55023: Issue with CP empty folder after y2038 on 32-bits Kernel
Date: Thu, 21 Apr 2022 21:59:04 +0100

On 21/04/2022 18:41, Adhemerval Zanella wrote:
> 
> 
> On 21/04/2022 12:25, Pádraig Brady wrote:
>> On 21/04/2022 15:53, Arnaud Panaïotis wrote:
>>>
>>> On 21/04/2022 14:36, Pádraig Brady wrote:
>>>> On 19/04/2022 16:01, Arnaud Panaïotis wrote:
>>>>> On 19/04/2022 16:00, Pádraig Brady wrote:
>>>>>> On 19/04/2022 08:47, Arnaud Panaïotis wrote:
>>>>>>> Hello,
>>>>>>>
>>>>>>> I did not received any feedback from this request right now. Have you
>>>>>>> made any progress on this subject ?
>>>>>>>
>>>>>>> Please let me know the progress for this, or contact me for additional
>>>>>>> information if needed.
>>>>>>>
>>>>>>> I'd like to have a ticket link to follow the advancement of this issue
>>>>>>> (if possible). I'm available to test a patch if you are able to provide
>>>>>>> me one.
>>>>>>>
>>>>>>> Best regards,
>>>>>>>
>>>>>>> On 01/04/2022 15:55, Arnaud Panaïotis wrote:
>>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> I'm working for a client to generate embedded 32-bits Linux Kernel
>>>>>>>> working after y2038 issue.
>>>>>>>>
>>>>>>>> I generated a 5.15 Kernel thought Buildroot with Coreutils 9.0, GCC
>>>>>>>> 11.2.0, Binutils 2.37 and CFLAGS  -D_LARGEFILE_SOURCE
>>>>>>>> -D_FILE_OFFSET_BITS=64  -D_TIME_BITS=64
>>>>>>>>
>>>>>>>> The Kernel pass y2038 but I found an issue with cp:
>>>>>>>> After analysis, the error occurs when trying to move an empty folder
>>>>>>>> without all user mode rights.
>>>>>>>>
>>>>>>>> Here how to reproduce:
>>>>>>>>
>>>>>>>> # mkdir -p test/test1 folder
>>>>>>>> # chmod u-w test/test1
>>>>>>>> # date -s "2040-04-02"
>>>>>>>> # cp -a test/* folder/
>>>>>>>> cp: setting permissions for 'folder/test1' : Value too large for defined data type
>>>>>>>>
>>>>>>>> Note: The folder is copied before the error occurs. The copy works
>>>>>>>> fine before y2038.
>>>>>>>>
>>>>>>>>
>>>>>>>> The issue comes from coreutils-9.0/src/cp.c
>>>>>>>>
>>>>>>>> Line 512 : if (lchmod (dir, stats.st_mode | S_IRWXU) != 0)
>>>>>>>>
>>>>>>>> FYI I had a previous issue while calling lstat function from
>>>>>>>> <sys/stat.h> which is included in lib/lchmod.c. I used /usr/bin/stat
>>>>>>>> as a workaround.
>>>>>>>>
>>>>>>>>
>>>>>>>> Keep me in touch if you need more information.
>>>>>>
>>>>>> The original mail seems to not have hit the lists, sorry.
>>>>>>
>>>>>> The error suggests that the fstatat() done within lchmod()
>>>>>> is using a 32 bit time_t component of the stat structure.
>>>>>> Your kernel is new enough to support the 64 bit equivalent,
>>>>>> but you don't mention glibc. Can you ensure you're using
>>>>>> at least glibc 2.34, which added support for the 64 bit variants.
>>>>>>
>>>>>> coreutils is configured by default to enable use
>>>>>> of the 64 bit variants where available, and you've confirmed
>>>>>> this as you say both -D_FILE_OFFSET_BITS=64 and -D_TIME_BITS=64 are defined.
>>>>>>
>>>>>> An strace of the cp command would be useful to confirm the problematic syscall.
>>>>
>>>> That suggests the kernel (statx) returns fine,
>>>> but glibc is returning the EOVERFLOW.
>>>> That suggests fstatat() rather than fstatat64() is being used
>>>> (inferring that by comparing
>>>> https://sourceware.org/git/?p=glibc.git;a=history;f=sysdeps/unix/sysv/linux/fstatat.c
>>>> https://sourceware.org/git/?p=glibc.git;a=history;f=sysdeps/unix/sysv/linux/fstatat64.c)
>>>>
>>>> So why is fstatat() being used if compiling with
>>>> -D_FILE_OFFSET_BITS=64 and -D_TIME_BITS=64
>>>>
>>>> You might confirm what statat is being called with:
>>>> nm cp | grep U.*statat
>>>>
>>>> The redirect from fstatat() in code to the appropriate 64 bit interface
>>>> should be done with asm redirects and so immune to any undef etc.
>>>> that gnulib may be doing.
>>>>
>>>> So in summary please look at how fstatat() is being referenced
>>>> on your system (by gnulib).
>>>>
>>>> thanks,
>>>> Pádraig
>>>
>>> Hi,
>>>
>>> I had to add -D option to nm to avoid "no symbols" error.
>>>
>>>           U __fstatat64_time64 <at> GLIBC_2.34
>>>
>>> All fstat, fstatat, lstat and stat are 64_time64 with the same GLIBC.
>>
>> That looks correct.
>>
>> So perhaps the EOVERFLOW is within your glibc's fstatat64 implementation?
>> You might get to the issue more quickly by installing debug symbols for
>> your coreutils and/or glibc and using: gdb -tui -args cp rest of cp args
>>
> 
> Assuming a default config option (without --enable-kernel) the
> _fstatat64_time64 should first try statx and then the old fstatat64
> if statx fails with ENOSYS (on kernel older than 4.11).  The EOVERFLOW
> only happens for later, assuming kernel does not returns anything
> bogus.
> 
> What strace shows in this scenario?

strace shows statx() returning non error on this 5.15 kernel

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