linux-kernel - [PATCH BUGFIX] kmod: Fix resource leak in call_usermodehelper

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Date:	Fri, 18 Dec 2009 12:07:00 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH BUGFIX] kmod: Fix resource leak in call_usermodehelper_pipe()

Fix resource (write-pipe file) leak in call_usermodehelper_pipe().

When call_usermodehelper_exec() is failed, write-pipe file is opened
and call_usermodehelper_pipe() just returns an error. Since it is
hard for caller to classify the error is occured when opening pipe
or executing helper, caller can't close the pipe by themselves.

I've found this resoruce leak when testing coredump.
You can check how the resource leaks as below;

$ echo "|nocommand" > /proc/sys/kernel/core_pattern
$ ulimit -c unlimited
$ while [ 1 ]; do ./segv; done &> /dev/null &
$ cat /proc/meminfo (<- repeat it)

where segv.c is;
//-----
int main () {
        char *p = 0;
        *p = 1;
}
//-----

This patch closes write-pipe file if call_usermodehelper_exec()
is failed.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---

 kernel/kmod.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 25b1031..bf0e231 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -520,13 +520,15 @@ int call_usermodehelper_pipe(char *path, char **argv, char **envp,
 		return -ENOMEM;
 
 	ret = call_usermodehelper_stdinpipe(sub_info, filp);
-	if (ret < 0)
-		goto out;
+	if (ret < 0) {
+		call_usermodehelper_freeinfo(sub_info);
+		return ret;
+	}
 
-	return call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
+	ret = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
+	if (ret < 0)	/* Failed to execute helper, close pipe */
+		filp_close(*filp, NULL);
 
-  out:
-	call_usermodehelper_freeinfo(sub_info);
 	return ret;
 }
 EXPORT_SYMBOL(call_usermodehelper_pipe);


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com
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