Re: [Bug-tar] infinite loop in sparse_dump_region()

[Pavel Raiskup]

Hi, the proposed patch [1] can still be applied, and the reproducer below is
still valid.  Please let me know I could fix something in the patch.

[1] https://www.mail-archive.com/address@hidden/msg04443.html

Pavel

On Sunday, March 16, 2014 10:55:38 PM CET Pavel Raiskup wrote:
> Hello François,
> 
> On Thursday, March 13, 2014 14:43:55 François Ouellet wrote:
> > When dumping a file which is being actively updated by an application
> > (in our case it was an outlook pst file on our samba server), safe_read()
> > can sometimes return 0.
> > 
> > When it happens, sparse_dump_region() goes into an infinite loop.
> > 
> > I don't know what the proper fix would be.  I just fixed it on our server
> > with this:
> 
> thanks for clear report!  You can try the attached patch if you wanted (but it
> has the same effects as yours one, just the message is little bit different).
> Reproducer:
> 
>   $ truncate -s 10M file
>   $ tar cSf archive file
>   $ truncate -s 5M file
>   $ tar df archive
> 
> Could we please apply at least something like the patch attached?
> Looking at the code, I don't like duplications.  I was thinking
> about safe_read/blocking_read wrapper with sth. like 'bool may_eof'
> argument (and others) to make it possible to deal with errors at one
> place (stopped once I realized that it will be somehow bigger code
> change).  Would you be interested in such patch?
> 
> Pavel