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Date: Sat, 22 Jun 2024 20:37:31 +0200
From: Florian Ziesche <florian.ziesche@...il.com>
To: Rich Felker <dalias@...c.org>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] dynlink: fix get_lfs64() with posix_fallocate64

Yep, this works for me.

> On 22. Jun 2024, at 03:06, Rich Felker <dalias@...c.org> wrote:
> 
> On Thu, May 23, 2024 at 04:28:03PM -0400, Rich Felker wrote:
>> On Fri, May 10, 2024 at 06:01:58PM +0200, Florian Ziesche wrote:
>>> Hi,
>>> 
>>> this patch increases the buffer size by one in get_lfs64() so that it
>>> works with posix_fallocate64.
>>> "posix_fallocate64" is 17 characters long, so 16 is one too short.
>>> 
>>> Simplified example:
>>> before: https://compiler-explorer.com/z/4qcPhcaWr
>>> after: https://compiler-explorer.com/z/scGvhddKW
>>> 
>>> ---
>>> diff --git a/ldso/dynlink.c b/ldso/dynlink.c
>>> index 42687da2..8707ae1c 100644
>>> --- a/ldso/dynlink.c
>>> +++ b/ldso/dynlink.c
>>> @@ -363,7 +363,7 @@ static struct symdef get_lfs64(const char *name)
>>>         "stat\0statfs\0statvfs\0tmpfile\0truncate\0versionsort\0"
>>>         "__fxstat\0__fxstatat\0__lxstat\0__xstat\0";
>>>     size_t l;
>>> -    char buf[16];
>>> +    char buf[17];
>>>     for (l=0; name[l]; l++) {
>>>         if (l >= sizeof buf) goto nomatch;
>>>         buf[l] = name[l];
>> 
>> Thanks for catching this. I questioned whether the 17 is sufficient,
>> but indeed the buffer is never nul terminated except when removing the
>> 64, so it should be ok.
>> 
>> I think I'll apply your patch as a direct fix, but the whole copying
>> operation is unnecessary and I'll probably remove it. It works just as
>> well to strncmp and pass p instead of buf to find_sym, so that a
>> mutable copy of the name to lookup is never needed.
> 
> Applied. Does the attached look ok to get rid of the copy entirely? It
> passed basic smoke testing here.
> 
> <get_lfs64.diff>


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