Re: [PATCH 01/11] mingw: avoid accessing uninitialized memory in `is_executable()`

From: Junio C Hamano <gitster@pobox.com>
To: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: Re: [PATCH 01/11] mingw: avoid accessing uninitialized memory in `is_executable()`
Date: Wed, 15 Jun 2022 21:07:05 -0700	[thread overview]
Message-ID: <xmqqk09hxndi.fsf@gitster.g> (raw)
In-Reply-To: <679ea7421f73ce41515aca549982233f88bcefef.1655336146.git.gitgitgadget@gmail.com> (Johannes Schindelin via GitGitGadget's message of "Wed, 15 Jun 2022 23:35:35 +0000")

"Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
writes:

> From: Johannes Schindelin <johannes.schindelin@gmx.de>
>
> On Windows, we open files we suspect might be scripts, read the first
> two bytes, and see whether they indicate a hash-bang line. We do not
> initialize the byte _after_ those two bytes, therefore `strcmp()` is
> inappropriate here.
>
> Reported by Coverity.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>  run-command.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

This has been with us since cc3b7a97 (Windows: Make 'git help -a'
work., 2008-01-14) and apparently nobody made loud enough noises
to make us aware since then.

The fix is trivially correct, of course.

Will queue.

>
> diff --git a/run-command.c b/run-command.c
> index 14f17830f51..2ba38850b4d 100644
> --- a/run-command.c
> +++ b/run-command.c
> @@ -154,7 +154,7 @@ int is_executable(const char *name)
>  		n = read(fd, buf, 2);
>  		if (n == 2)
>  			/* look for a she-bang */
> -			if (!strcmp(buf, "#!"))
> +			if (!memcmp(buf, "#!", 2))
>  				st.st_mode |= S_IXUSR;
>  		close(fd);
>  	}