Re: [Bug-tar] Tar short read

[Andreas Dilger]

On 2011-09-27, at 2:38 PM, Andreas Dilger wrote:
> On 2011-09-27, at 1:48 PM, Sergey Poznyakoff wrote:
>> Kevin Fox <address@hidden> ha escrit:
>> 
>>> Thats not how I read that function:
>>> size_t safe_rw (int fd, void const *buf, size_t count)
>>> {
>>> enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 };
>>> for (;;)
>>>   {
>>>     ssize_t result = rw (fd, buf, count);
>>>     if (0 <= result)
>>>       return result;
>>> 
>>> short read, return right away without looping. I don't believe tar
>> 
>> You seem to confuse "short reads" with "interrupted reads".  A "short
>> read" is when read returns less bytes than requested.  No signals are
>> delivered it this case.  An "interrupted read" occurs when a signal is
>> delivered while read is in progress.  In that case read returns -1 and
>> sets errno to EINTR.  That's exactly what this function is designed to
>> handle.
> 
> In addition to Kevin's recent comments, I also noticed in the SUSv2
> description of read(2):
> 
>  http://pubs.opengroup.org/onlinepubs/007908799/xsh/read.html
> 
>  "If the value of nbyte is greater than {SSIZE_MAX}, the result
>   is implementation-dependent."
> 
> Attached is an (untested) patch for fixing these issues.  Maybe
> Kevin can give this a spin?

My bad, attached is a better patch (still untested, but fixes a
thinko that I'd meant to fix before sending):


Cheers, Andreas

safe-short-read.diff
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