From: Jeff King <peff@peff.net>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: Thomas Gummerer <t.gummerer@gmail.com>,
git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
"brian m. carlson" <sandals@crustytoothpaste.ath.cx>
Subject: Re: [PATCH 2/3] http-push: fix construction of hex value from path
Date: Tue, 3 Oct 2017 19:36:38 -0400 [thread overview]
Message-ID: <20171003233638.fq6lgls2qsucfbn3@sigill.intra.peff.net> (raw)
In-Reply-To: <20171003225315.GE19555@aiede.mtv.corp.google.com>
On Tue, Oct 03, 2017 at 03:53:15PM -0700, Jonathan Nieder wrote:
> Thomas Gummerer wrote:
>
> > The get_oid_hex_from_objpath takes care of creating a oid from a
> > pathname. It does this by memcpy'ing the first two bytes of the path to
> > the "hex" string, then skipping the '/', and then copying the rest of the
> > path to the "hex" string. Currently it fails to increase the pointer to
> > the hex string, so the second memcpy invocation just mashes over what
> > was copied in the first one, and leaves the last two bytes in the string
> > uninitialized.
>
> Wow. The fix is obviously correct.
Agreed. This is brown-paper-bag worthy. Thanks, Thomas, for cleaning up
my mess.
> I think the problem is that when it fails, we end up thinking that
> there are *fewer* objects than are actually present remotely so the
> only ill effect is pushing too much. So this should be observable in
> server logs (i.e. it is testable) but it's not a catastrophic failure
> which means it's harder to test than it would be otherwise.
And thank you, Jonathan, for this analysis. I had also wondered how such
a frequently-triggered bug could have gone completely unnoticed, but
this explains it.
> Moreover, this is in the webdav-based "dumb http" push code path,
> which I do not trust much at all. I wonder if we could retire it
> completely (or at least provide an option to turn it off).
I would really like that, too. It has been the cause of a lot of pain
when working with the smart code, and I am not at all surprised to find
a bug of this magnitude lurking in it. I'd _hoped_ this could show that
the system has been unusably broken for years, which would give us
confidence to turn it off. :) But per your paragraph above, people could
very easily still have been happily using it in the meantime.
-Peff
next prev parent reply other threads:[~2017-10-03 23:36 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-03 19:57 [PATCH 0/3] fixes for running the test suite with --valgrind Thomas Gummerer
2017-10-03 19:57 ` [PATCH 1/3] path.c: fix uninitialized memory access Thomas Gummerer
2017-10-03 22:45 ` Jonathan Nieder
2017-10-03 23:30 ` Jeff King
2017-10-03 23:37 ` Jonathan Nieder
2017-10-04 4:47 ` Junio C Hamano
2017-10-04 5:21 ` Jeff King
2017-10-04 19:22 ` Thomas Gummerer
2017-10-04 19:36 ` Jonathan Nieder
2017-10-03 19:57 ` [PATCH 2/3] http-push: fix construction of hex value from path Thomas Gummerer
2017-10-03 22:53 ` Jonathan Nieder
2017-10-03 23:36 ` Jeff King [this message]
2017-10-04 4:48 ` Junio C Hamano
2017-10-04 5:20 ` Junio C Hamano
2017-10-04 5:26 ` Jeff King
2017-10-04 6:26 ` Junio C Hamano
2017-10-03 19:57 ` [PATCH 3/3] sub-process: allocate argv on the heap Thomas Gummerer
2017-10-03 20:24 ` Johannes Sixt
2017-10-04 4:59 ` Junio C Hamano
2017-10-04 5:32 ` Jeff King
2017-10-04 5:58 ` Johannes Sixt
2017-10-04 19:31 ` Thomas Gummerer
2017-10-03 20:25 ` Stefan Beller
2017-10-03 23:41 ` [PATCH 0/3] fixes for running the test suite with --valgrind Jeff King
2017-10-03 23:50 ` Jonathan Nieder
2017-10-03 23:54 ` Jeff King
2017-10-04 10:19 ` playing with MSan, was " Jeff King
2017-10-04 19:30 ` Thomas Gummerer
2017-10-05 3:46 ` lstat-ing delayed-filter output, was Re: playing with MSan Jeff King
2017-10-05 10:47 ` Lars Schneider
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