From: demerphq <demerphq@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Git <git@vger.kernel.org>, "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: Bug: git branch --unset-upstream command can nuke config when disk is full.
Date: Wed, 13 Sep 2017 17:49:14 +0200 [thread overview]
Message-ID: <CANgJU+XyfeDCpdZTKJOppjs6w6zS1kjxDAwbvOZr_1a8Fyqe7Q@mail.gmail.com> (raw)
In-Reply-To: <20170913152205.sw3i5xzsynx62nea@sigill.intra.peff.net>
On 13 September 2017 at 17:22, Jeff King <peff@peff.net> wrote:
> On Wed, Sep 13, 2017 at 05:18:56PM +0200, demerphq wrote:
>
>> > Hmph. That is very disturbing. But with that information I should be
>> > able to track down the culprit. Thanks for digging.
>>
>> FWIW, I see that git_config_set_multivar_in_file_gently() uses
>> write_in_full() which in turn uses xwrite(), but the latter has the
>> following comment on it:
>>
>> /*
>> * xwrite() is the same a write(), but it automatically restarts write()
>> * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT
>> * GUARANTEE that "len" bytes is written even if the operation is successful.
>> */
>>
>> I suspect that at this point I am not adding much value here, so I
>> will leave it at this.
>
> No, the problem is in this line:
>
> if (write_in_full(fd, contents + copy_begin,
> copy_end - copy_begin) <
> copy_end - copy_begin)
> goto write_err_out;
>
> write_in_full() returns -1 on error (_not_ how many bytes were actually
> written). So its return is a signed ssize_t. But the result of the
> pointer subtraction "copy_end - copy_begin" is an unsigned ptrdiff_t.
> The compiler promotes the signed to an unsigned, so the condition can
> never be true (the "-1" becomes the highest possible value).
Bah. Good eye. I missed that entirely.
> I have the fix, but I'm searching the code base for other instances of
> the same error.
Yeah, I think there are few just in that file.
Thanks for fixing this!
cheers,
Yves
--
perl -Mre=debug -e "/just|another|perl|hacker/"
next prev parent reply other threads:[~2017-09-13 15:49 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-13 11:59 Bug: git branch --unset-upstream command can nuke config when disk is full demerphq
2017-09-13 12:34 ` Jeff King
2017-09-13 13:38 ` demerphq
2017-09-13 14:17 ` Jeff King
2017-09-13 14:49 ` demerphq
2017-09-13 14:51 ` Jeff King
2017-09-13 15:18 ` demerphq
2017-09-13 15:22 ` Jeff King
2017-09-13 15:49 ` demerphq [this message]
2017-09-13 17:08 ` [PATCH 0/7] config.c may fail to notice some write() failures Jeff King
2017-09-13 17:11 ` [PATCH 1/7] config: avoid "write_in_full(fd, buf, len) < len" pattern Jeff King
2017-09-13 17:47 ` Jonathan Nieder
2017-09-13 17:53 ` Jeff King
2017-09-13 17:59 ` Jonathan Nieder
2017-09-13 18:11 ` Jeff King
2017-09-13 18:15 ` [PATCH v2] " Jeff King
2017-09-13 18:24 ` Jonathan Nieder
2017-09-13 18:58 ` Jeff King
2017-09-13 19:18 ` Jonathan Nieder
2017-09-13 19:49 ` Jonathan Nieder
2017-09-13 22:43 ` Ramsay Jones
2017-09-13 23:31 ` Ramsay Jones
2017-09-15 0:37 ` Jeff King
2017-09-15 15:15 ` Ramsay Jones
2017-09-13 21:33 ` Junio C Hamano
2017-09-13 17:11 ` [PATCH 2/7] get-tar-commit-id: check write_in_full() return against 0 Jeff King
2017-09-13 17:53 ` Jonathan Nieder
2017-09-13 18:02 ` Jeff King
2017-09-13 18:37 ` Jeff King
2017-09-13 21:09 ` Jonathan Nieder
2017-09-15 0:40 ` Jeff King
2017-09-13 17:16 ` [PATCH 3/7] avoid "write_in_full(fd, buf, len) != len" pattern Jeff King
2017-09-13 21:14 ` Jonathan Nieder
2017-09-15 0:42 ` Jeff King
2017-09-13 17:16 ` [PATCH 4/7] convert less-trivial versions of "write_in_full() != len" Jeff King
2017-09-13 21:16 ` Jonathan Nieder
2017-09-13 17:17 ` [PATCH 5/7] pkt-line: check write_in_full() errors against "< 0" Jeff King
2017-09-13 21:17 ` Jonathan Nieder
2017-09-13 17:17 ` [PATCH 6/7] notes-merge: use ssize_t for write_in_full() return value Jeff King
2017-09-13 21:20 ` Jonathan Nieder
2017-09-15 0:43 ` Jeff King
2017-09-13 17:17 ` [PATCH 7/7] config: flip return value of store_write_*() Jeff King
2017-09-13 21:25 ` Jonathan Nieder
2017-09-15 0:46 ` Jeff King
2017-09-13 18:47 ` [PATCH 8/7] read_pack_header: handle signed/unsigned comparison in read result Jeff King
2017-09-13 19:11 ` Jonathan Nieder
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