From: Junio C Hamano <gitster@pobox.com>
To: "René Scharfe" <l.s.r@web.de>
Cc: Git List <git@vger.kernel.org>
Subject: Re: [PATCH] pkt-line: don't check string length in packet_length()
Date: Wed, 05 Jul 2023 15:27:24 -0700 [thread overview]
Message-ID: <xmqqsfa2uh83.fsf@gitster.g> (raw)
In-Reply-To: <6f984150-5a98-b2b8-1791-b101f5953b7a@web.de> ("René Scharfe"'s message of "Wed, 5 Jul 2023 23:11:15 +0200")
René Scharfe <l.s.r@web.de> writes:
> Sure, that's done. If any of the four characters is not a hexadecimal
> digit then packet_length() returns a negative value, before and after
> the change.
Ah, it is the beauty of hexval[] table ;-)
So as long as we are sure that we are not running beyond the end of
the buffer, we are OK. And as I already said, I think "this change
is safe for our two callers; those adding more callers in the future
are better be very careful" is probably good enough for this one.
hex.h:hex2chr() says "don't run over the end of short strings", but
as far as I can see it does not check any such thing; find a page of
memory, whose next page is unmapped, and pointing *s at the last
byte of that page and calling it will happily run over the end and
would cause SIGBUS. The function assumes that such a short string
is always NUL terminated, which is not a great way to guarantee that
we do not run over the end of strings.
next prev parent reply other threads:[~2023-07-05 22:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-01 7:05 [PATCH] pkt-line: don't check string length in packet_length() René Scharfe
2023-07-05 5:56 ` Junio C Hamano
2023-07-05 16:15 ` René Scharfe
2023-07-05 20:33 ` Junio C Hamano
2023-07-05 21:11 ` René Scharfe
2023-07-05 22:27 ` Junio C Hamano [this message]
2023-07-06 5:07 ` René Scharfe
2023-07-07 21:47 ` [PATCH v2] pkt-line: add size parameter to packet_length() René Scharfe
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