From: Paolo Bonzini <bonzini@gnu•org>
To: Johannes Sixt <j.sixt@viscovery•net>
Cc: Karl Chen <quarl@cs•berkeley.edu>,
Git mailing list <git@vger•kernel.org>,
Junio C Hamano <gitster@pobox•com>
Subject: [PATCH] be paranoid about closed stdin/stdout/stderr
Date: Tue, 26 Aug 2008 08:48:35 +0200 [thread overview]
Message-ID: <E1KXsL9-0004ef-Co@fencepost.gnu.org> (raw)
In-Reply-To: <7vbpzgb94q.fsf@gitster.siamese.dyndns.org>
It is in general unsafe to start git with one or more of file descriptors
0/1/2 closed. Karl Chen for example noticed that stat_command does this
in order to rename a pipe file descriptor to 0:
dup2(from, 0);
close(from);
... but if stdin was closed (for example) from == 0, so that
dup2(0, 0);
close(0);
just ends up closing the pipe. Another extremely rare but nasty problem
would occur if an "important" file ends up in file descriptor 2, and is
corrupted by a call to die().
This patch fixes these problems by opening all of the "low" descriptors
to /dev/null in main.
Signed-off-by: Paolo Bonzini <bonzini@gnu•org>
---
git.c | 13 +++++++++++++
1 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/git.c b/git.c
index 89e4645..be227b2 100644
--- a/git.c
+++ b/git.c
@@ -420,6 +420,19 @@ int main(int argc, const char **argv)
const char *cmd = argv[0] && *argv[0] ? argv[0] : "git-help";
char *slash = (char *)cmd + strlen(cmd);
int done_alias = 0;
+ int devnull_fd;
+
+ /*
+ * Always open file descriptors 0/1/2 to avoid clobbering files
+ * in die(). It also avoids not messing up when the pipes are
+ * dup'ed onto stdin/stdout/stderr in the child processes we spawn.
+ */
+ devnull_fd = open("/dev/null", O_RDWR);
+ while (devnull_fd >= 0 && devnull_fd <= 2)
+ devnull_fd = dup(devnull_fd);
+ if (devnull_fd == -1)
+ die("opening /dev/null failed (%s)", strerror(errno));
+ close (devnull_fd);
/*
* Take the basename of argv[0] as the command
--
1.5.5
next prev parent reply other threads:[~2008-08-26 6:50 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-25 8:28 [PATCH] Fix start_command() pipe bug when stdin is closed Karl Chen
2008-08-25 10:44 ` Johannes Sixt
2008-08-25 11:49 ` Paolo Bonzini
2008-08-25 12:00 ` [PATCH v2] fix start_command() " Paolo Bonzini
2008-08-25 13:12 ` Johannes Sixt
2008-08-25 13:37 ` [PATCH v2 properly indented] " Paolo Bonzini
2008-08-25 16:00 ` Karl Chen
2008-08-26 0:06 ` Junio C Hamano
2008-08-26 6:09 ` Junio C Hamano
2008-08-26 6:33 ` Johannes Sixt
2008-08-26 6:45 ` Paolo Bonzini
2008-08-26 6:48 ` Paolo Bonzini [this message]
2008-08-26 6:57 ` [PATCH] be paranoid about closed stdin/stdout/stderr Johannes Sixt
2008-08-26 7:40 ` Stephen R. van den Berg
2008-08-27 5:01 ` Avery Pennarun
2008-08-27 9:18 ` Stephen R. van den Berg
2008-08-27 12:36 ` Paolo Bonzini
2008-08-27 15:20 ` [PATCH v4] make git-shell " Paolo Bonzini
2008-08-27 17:22 ` Stephen R. van den Berg
2008-08-27 17:27 ` [PATCH] be " Junio C Hamano
2008-08-28 13:17 ` Paolo Bonzini
2008-08-28 13:58 ` Stephen R. van den Berg
2008-08-27 18:22 ` Avery Pennarun
2008-08-28 12:21 ` Nick Andrew
2008-08-28 12:52 ` Stephen R. van den Berg
2008-08-26 17:38 ` Junio C Hamano
2008-08-26 18:33 ` Paolo Bonzini
2008-08-26 22:42 ` Junio C Hamano
2008-08-26 23:04 ` Junio C Hamano
2008-08-26 23:10 ` Stephen R. van den Berg
2008-08-27 3:05 ` Karl Chen
2008-08-27 4:38 ` Paolo Bonzini
2008-08-27 9:04 ` Stephen R. van den Berg
2008-08-27 6:35 ` Johannes Sixt
2008-08-27 8:20 ` Paolo Bonzini
2008-08-27 2:04 ` Nick Andrew
2008-08-25 15:56 ` [PATCH] Fix start_command() pipe bug when stdin is closed Karl Chen
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