linux-kernel - [22/65] cap_syslog: dont use WARN_ONCE for CAP_SYS

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Date:	Wed, 01 Feb 2012 12:56:02 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Ralf Hildebrandt <ralf.hildebrandt@...rite.de>,
	Niels <zorglub_olsen@...mail.com>,
	Paweł Sikora <pluto@...k.net>,
	Jonathan Nieder <jrnieder@...il.com>,
	Serge Hallyn <serge@...lyn.com>,
	James Morris <jmorris@...ei.org>,
	Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>
Subject: [22/65] cap_syslog: dont use WARN_ONCE for CAP_SYS_ADMIN
 deprecation warning

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jonathan Nieder <jrnieder@...il.com>

commit f2c0d0266cc5eb36a4aa44944b4096ec121490aa upstream.

syslog-ng versions before 3.3.0beta1 (2011-05-12) assume that
CAP_SYS_ADMIN is sufficient to access syslog, so ever since CAP_SYSLOG
was introduced (2010-11-25) they have triggered a warning.

Commit ee24aebffb75 ("cap_syslog: accept CAP_SYS_ADMIN for now")
improved matters a little by making syslog-ng work again, just keeping
the WARN_ONCE().  But still, this is a warning that writes a stack trace
we don't care about to syslog, sets a taint flag, and alarms sysadmins
when nothing worse has happened than use of an old userspace with a
recent kernel.

Convert the WARN_ONCE to a printk_once to avoid that while continuing to
give userspace developers a hint that this is an unwanted
backward-compatibility feature and won't be around forever.

Reported-by: Ralf Hildebrandt <ralf.hildebrandt@...rite.de>
Reported-by: Niels <zorglub_olsen@...mail.com>
Reported-by: Paweł Sikora <pluto@...k.net>
Signed-off-by: Jonathan Nieder <jrnieder@...il.com>
Liked-by: Gergely Nagy <algernon@...house-project.org>
Acked-by: Serge Hallyn <serge@...lyn.com>
Acked-by: James Morris <jmorris@...ei.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/printk.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -318,8 +318,10 @@ static int check_syslog_permissions(int
 			return 0;
 		/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
 		if (capable(CAP_SYS_ADMIN)) {
-			WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
-				 "but no CAP_SYSLOG (deprecated).\n");
+			printk_once(KERN_WARNING "%s (%d): "
+				 "Attempt to access syslog with CAP_SYS_ADMIN "
+				 "but no CAP_SYSLOG (deprecated).\n",
+				 current->comm, task_pid_nr(current));
 			return 0;
 		}
 		return -EPERM;


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