Re: [Bug-tar] Tar short read

[Andreas Dilger]

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?

Cheers, Andreas

safe-read.diff
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