From: Junio C Hamano <gitster@pobox.com>
To: Simon Richter <Simon.Richter@hogyros.de>
Cc: Patrick Steinhardt <ps@pks.im>,
git@vger.kernel.org, Ben Knoble <ben.knoble@gmail.com>,
Jeff King <peff@peff.net>,
"brian m. carlson" <sandals@crustytoothpaste.net>,
"Randall S. Becker" <randall.becker@nexbridge.ca>,
Phillip Wood <phillip.wood@dunelm.org.uk>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH 1/5] compat/posix: introduce writev(3p) wrapper
Date: Thu, 16 Jul 2026 13:09:32 -0700 [thread overview]
Message-ID: <xmqqfr1ig0hv.fsf@gitster.g> (raw)
In-Reply-To: <a2676ec6-39d5-4220-8549-10a17daec668@hogyros.de> (Simon Richter's message of "Thu, 16 Jul 2026 17:47:25 +0900")
Simon Richter <Simon.Richter@hogyros.de> writes:
> Hi,
>
>> + if (iov[i].iov_len > maximum_signed_value_of_type(ssize_t) ||
>> + iov[i].iov_len + sum > maximum_signed_value_of_type(ssize_t)) {
>
> That feels like it could overflow.
Isn't it checking if it would overflow (and dying if so)?
Ah, wait. The addition "(iov[i].iov_len + sum)" can indeed wrap
around, and comparing it with the maximum value of ssize_t wouldn't
catch that. Is that what you mean?
Would something like this:
if (maximum_signed_value_of_type(ssize_t) < iov[i].iov_len ||
iov[i].iov_len + sum < iov[i].iov_len ||
maximum_signed_value_of_type(ssize_t) < iov[i].iov_len + sum)
work better to catch the three cases independently?
(1) The value is already too large on its own.
(2) Adding them together would cause an unsigned wrap-around.
(3) The sum does not wrap around, but it exceeds the maximum
representable value of ssize_t anyway.
next prev parent reply other threads:[~2026-07-16 20:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-16 7:52 [PATCH 0/5] Reintroduce writev(3p) Patrick Steinhardt
2026-07-16 7:52 ` [PATCH 1/5] compat/posix: introduce writev(3p) wrapper Patrick Steinhardt
2026-07-16 8:47 ` Simon Richter
2026-07-16 20:09 ` Junio C Hamano [this message]
2026-07-16 20:44 ` Junio C Hamano
2026-07-16 7:52 ` [PATCH 2/5] wrapper: introduce writev(3p) wrappers Patrick Steinhardt
2026-07-16 7:52 ` [PATCH 3/5] wrapper: properly handle MAX_IO_SIZE in writev(3p) Patrick Steinhardt
2026-07-16 7:52 ` [PATCH 4/5] sideband: use writev(3p) to send pktlines Patrick Steinhardt
2026-07-16 7:52 ` [PATCH 5/5] fast-import: use writev(3p) to send cat-blob responses Patrick Steinhardt
2026-07-16 18:56 ` [PATCH 0/5] Reintroduce writev(3p) Johannes Sixt
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