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From: Jonathan Nieder <jrnieder@gmail.com>
To: David Turner <dturner@twosigma.com>
Cc: git@vger.kernel.org, l.s.r@web.de
Subject: Re: [PATCH v3 2/2] xgethostname: handle long hostnames
Date: Tue, 18 Apr 2017 18:35:52 -0700	[thread overview]
Message-ID: <20170419013552.GB28740@aiede.svl.corp.google.com> (raw)
In-Reply-To: <20170418215743.18406-3-dturner@twosigma.com>

Hi,

David Turner wrote:

> If the full hostname doesn't fit in the buffer supplied to
> gethostname, POSIX does not specify whether the buffer will be
> null-terminated, so to be safe, we should do it ourselves.  Introduce
> new function, xgethostname, which ensures that there is always a \0
> at the end of the buffer.

I think we should detect the error instead of truncating the hostname.
That (on top of your patch) would look like the following.

Thoughts?
Jonathan

diff --git i/wrapper.c w/wrapper.c
index d837417709..e218bd3bef 100644
--- i/wrapper.c
+++ w/wrapper.c
@@ -660,11 +660,13 @@ int xgethostname(char *buf, size_t len)
 {
 	/*
 	 * If the full hostname doesn't fit in buf, POSIX does not
-	 * specify whether the buffer will be null-terminated, so to
-	 * be safe, do it ourselves.
+	 * guarantee that an error will be returned. Check for ourselves
+	 * to be safe.
 	 */
 	int ret = gethostname(buf, len);
-	if (!ret)
-		buf[len - 1] = 0;
+	if (!ret && !memchr(buf, 0, len)) {
+		errno = ENAMETOOLONG;
+		return -1;
+	}
 	return ret;
 }

  reply	other threads:[~2017-04-19  1:35 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-18 21:57 [PATCH v3 0/2] gethostbyname fixes David Turner
2017-04-18 21:57 ` [PATCH v3 1/2] use HOST_NAME_MAX to size buffers for gethostname(2) David Turner
2017-04-19  1:28   ` Jonathan Nieder
2017-04-19  2:57     ` Junio C Hamano
2017-04-19 14:03     ` René Scharfe
2017-04-19 17:28     ` René Scharfe
2017-04-19 19:08       ` David Turner
2017-04-19 19:09       ` Torsten Bögershausen
2017-04-19 20:02         ` René Scharfe
2017-04-20 18:37           ` Torsten Bögershausen
2017-04-20 19:28             ` René Scharfe
2017-04-21  4:18               ` Torsten Bögershausen
2017-04-18 21:57 ` [PATCH v3 2/2] xgethostname: handle long hostnames David Turner
2017-04-19  1:35   ` Jonathan Nieder [this message]
2017-04-19  2:51     ` Junio C Hamano
2017-04-19 15:50       ` David Turner
2017-04-19 16:43         ` René Scharfe
2017-04-19  2:48   ` Junio C Hamano

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