RFR(xs): (jdk10) 8173828: realpath is unsafe

Wed Mar 15 08:41:12 UTC 2017

Hi all,

thanks for the reviews. I addressed the remaining issues:

webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8173828-realpath-is-unsafe/jdk10-webrev.03/webrev/
Delta to last:
http://cr.openjdk.java.net/~stuefe/webrevs/8173828-realpath-is-unsafe/jdk10-webrev.02-to-03.diff

Thanks for the thumbs up. Interesting that no-one commented on the
guarantee in case of an overwrite, you are all ok with it? Thought about
using an assert, but I do not really want the production VM to ignore
overwrites.

Kind Regards, Thomas

On Wed, Mar 15, 2017 at 8:30 AM, Langer, Christoph <christoph.langer at sap.com
> wrote:

> Hi Thomas,
>
> apart from David's findings I have only to add that the copyright year in
> os_posix.cpp should be updated as well.
>
> +1 from me.
>
> Best regards
> Christoph
>
> > -----Original Message-----
> > From: hotspot-runtime-dev [mailto:hotspot-runtime-dev-
> > bounces at openjdk.java.net] On Behalf Of David Holmes
> > Sent: Mittwoch, 15. März 2017 02:18
> > To: Thomas Stüfe <thomas.stuefe at gmail.com>; Dmitry Samersoff
> > <dmitry.samersoff at oracle.com>
> > Cc: hotspot-runtime-dev at openjdk.java.net
> > Subject: Re: RFR(xs): (jdk10) 8173828: realpath is unsafe
> >
> > Hi Thomas,
> >
> > Generally looks good. A few minor comments below.
> >
> > On 15/03/2017 12:36 AM, Thomas Stüfe wrote:
> > > Hi Dmitry,
> > >
> > > new webrev:
> > > http://cr.openjdk.java.net/~stuefe/webrevs/8173828-realpath-is-
> > unsafe/jdk10-webrev.02/webrev/
> >
> > os_solaris.cpp:
> >
> > +   char* rp = NULL;
> >
> > This new local variable seems unused.
> >
> > ---
> >
> > src/os/posix/vm/os_posix.hpp
> >
> > The comments are a little confusing:
> >
> > +   // On success, it will return a pointer to the input buffer.
> > +   // On error, it will return NULL and set errno. Content of output
> > buffer is undefined.
> > +   // On truncation error (output buffer too small), it will return
> > NULL and set errno to ENAMETOOLONG.
> >
> > Is it an input buffer or an output buffer? I think we are inputting an
> > output buffer :) Perhaps:
> >
> > // On success, returns 'outbuf', which now contains the path.
> > // On error, it will return NULL and set errno. The content of 'outbuf'
> > is undefined.
> > // On truncation error ( 'outbuf' too small), it will return NULL and
> > set errno to ENAMETOOLONG.
> >
> > ---
> >
> > src/os/posix/vm/os_posix.cpp
> >
> > Grammatical nit:
> >
> > +     // that it complains about the NULL we did hand down as user
> buffer.
> >
> > change to
> >
> > +     // that it complains about the NULL we handed down as the user
> buffer.
> >
> > Nit:
> >
> > +     // a memory overwriter.
> > +         guarantee(outbuf[outbuflen - 1] == '\0', "realpath buffer
> > overwriter detected.");
> >
> > overwiter -> overwite
> >
> > ---
> >
> > Thanks,
> > David
> > -----
> >
> >
> > > Fixed both issues. Note that os::jvm_path() does not have a way to
> signal
> > > errors back to the caller. os::jvm_path has a number of issues and
> could
> > > benefit from a cleanup, but this is outside the scope of this fix.
> > >
> > > Thanks, Thomas
> > >
> > >
> > > On Tue, Mar 14, 2017 at 12:30 PM, Dmitry Samersoff <
> > > dmitry.samersoff at oracle.com> wrote:
> > >
> > >> Thomas,
> > >>
> > >>> thank you for the review. These are good points, I addressed them
> all:
> > >>
> > >> os_posix.cpp:
> > >>
> > >>   1110: it's better to write as outbuf == NULL
> > >>
> > >> os_solaris.cpp:
> > >>
> > >>   2037: return value of realpath is not checked. Could you fix it as
> well?
> > >>
> > >> -Dmitry
> > >>
> > >>
> > >> On 2017-03-14 14:19, Thomas Stüfe wrote:
> > >>> Hi Dmitry,
> > >>>
> > >>> thank you for the review. These are good points, I addressed them
> all:
> > >>>
> > >>> New
> > >>> webrev: http://cr.openjdk.java.net/~stuefe/webrevs/8173828-
> > >> realpath-is-unsafe/jdk10-webrev.01/webrev/
> > >>> Delta to
> > >>> last: http://cr.openjdk.java.net/~stuefe/webrevs/8173828-
> > >> realpath-is-unsafe/jdk10-webrev.00-to-01/webrev/
> > >>>
> > >>> Thanks, Thomas
> > >>>
> > >>> On Tue, Mar 14, 2017 at 10:00 AM, Dmitry Samersoff
> > >>> <dmitry.samersoff at oracle.com
> > <mailto:dmitry.samersoff at oracle.com>>
> > >> wrote:
> > >>>
> > >>>     Thomas,
> > >>>
> > >>>     os_posix.cpp:
> > >>>
> > >>>     1121: It might be better to return ENAMETOOLONG
> > >>>
> > >>>     1131: It might be better to check for
> > >>>           filename != NULL && outbuf != NULL before any call to
> realpath
> > >>>           and return EINVAL for product and assert it for debug
> build.
> > >>>
> > >>>     1134: What is the goal of this assert? Do you see this problem?
> > >>>
> > >>>     1135: If realpath overwrites outbuf, strlen might have
> unpredictable
> > >>>           effect.
> > >>>
> > >>>           So it might be better to set last byte of outbuf to 0
> before
> > >>>           call to realpath and check that it is still zero after call
> > >>>
> > >>>     -Dmitry
> > >>>
> > >>>     On 2017-03-14 10:11, Thomas Stüfe wrote:
> > >>>     > Hi all,
> > >>>     >
> > >>>     > may I have reviews for this smallish fix.
> > >>>     >
> > >>>     > Issue: https://bugs.openjdk.java.net/browse/JDK-8173828
> > >>>     <https://bugs.openjdk.java.net/browse/JDK-8173828>
> > >>>     > Webrev:
> > >>>     >
> > >>>     http://cr.openjdk.java.net/~stuefe/webrevs/8173828-
> > >> realpath-is-unsafe/jdk10-webrev.00/
> > >>>     <http://cr.openjdk.java.net/~stuefe/webrevs/8173828-
> > >> realpath-is-unsafe/jdk10-webrev.00/>
> > >>>     >
> > >>>     > In short, realpath(3) is unsafe the way it is traditionally
> used
> > >>>     (with a
> > >>>     > user buffer provided). It is safe if used in the new
> POSIX.1-2008
> > >>>     compliant
> > >>>     > way. To wrap this behavior, I added a new os::Posix::realpath()
> > >>>     function
> > >>>     > which takes a buffer and a buffer size (like a sane API would
> but
> > >> the
> > >>>     > ancient realpath() did not) and moved safe buffer handling into
> > >>>     this API.
> > >>>     >
> > >>>     > Kind Regards, Thomas
> > >>>     >
> > >>>
> > >>>
> > >>>     --
> > >>>     Dmitry Samersoff
> > >>>     Oracle Java development team, Saint Petersburg, Russia
> > >>>     * I would love to change the world, but they won't give me the
> > >> sources.
> > >>>
> > >>>
> > >>
> > >>
> > >> --
> > >> Dmitry Samersoff
> > >> Oracle Java development team, Saint Petersburg, Russia
> > >> * I would love to change the world, but they won't give me the
> sources.
> > >>
>