rpms/kernel/F-12 fix-race-in-tty_fasync-properly.patch, NONE, 1.1 kernel.spec, 1.2017, 1.2018

[Chuck Ebbert]

Author: cebbert

Update of /cvs/pkgs/rpms/kernel/F-12
In directory cvs1.fedora.phx.redhat.com:/tmp/cvs-serv28163

Modified Files:
	kernel.spec 
Added Files:
	fix-race-in-tty_fasync-properly.patch 
Log Message:
fix-race-in-tty_fasync-properly.patch: fix for deadlock caused
  by original patch in 2.6.32.6 

fix-race-in-tty_fasync-properly.patch:
 drivers/char/tty_io.c |    4 +++-
 fs/fcntl.c            |    6 ++----
 2 files changed, 5 insertions(+), 5 deletions(-)

--- NEW FILE fix-race-in-tty_fasync-properly.patch ---
>From 80e1e823989ec44d8e35bdfddadbddcffec90424 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds at linux-foundation.org>
Date: Sun, 7 Feb 2010 10:11:23 -0800
Subject: Fix race in tty_fasync() properly

From: Linus Torvalds <torvalds at linux-foundation.org>

commit 80e1e823989ec44d8e35bdfddadbddcffec90424 upstream.

This reverts commit 703625118069 ("tty: fix race in tty_fasync") and
commit b04da8bfdfbb ("fnctl: f_modown should call write_lock_irqsave/
restore") that tried to fix up some of the fallout but was incomplete.

It turns out that we really cannot hold 'tty->ctrl_lock' over calling
__f_setown, because not only did that cause problems with interrupt
disables (which the second commit fixed), it also causes a potential
ABBA deadlock due to lock ordering.

Thanks to Tetsuo Handa for following up on the issue, and running
lockdep to show the problem.  It goes roughly like this:

 - f_getown gets filp->f_owner.lock for reading without interrupts
   disabled, so an interrupt that happens while that lock is held can
   cause a lockdep chain from f_owner.lock -> sighand->siglock.

 - at the same time, the tty->ctrl_lock -> f_owner.lock chain that
   commit 703625118069 introduced, together with the pre-existing
   sighand->siglock -> tty->ctrl_lock chain means that we have a lock
   dependency the other way too.

So instead of extending tty->ctrl_lock over the whole __f_setown() call,
we now just take a reference to the 'pid' structure while holding the
lock, and then release it after having done the __f_setown.  That still
guarantees that 'struct pid' won't go away from under us, which is all
we really ever needed.

Reported-and-tested-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Acked-by: Greg Kroah-Hartman <gregkh at suse.de>
Acked-by: Américo Wang <xiyou.wangcong at gmail.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>

---
 drivers/char/tty_io.c |    4 +++-
 fs/fcntl.c            |    6 ++----
 2 files changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1930,8 +1930,10 @@ static int tty_fasync(int fd, struct fil
 			pid = task_pid(current);
 			type = PIDTYPE_PID;
 		}
-		retval = __f_setown(filp, pid, type, 0);
+		get_pid(pid);
 		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+		retval = __f_setown(filp, pid, type, 0);
+		put_pid(pid);
 		if (retval)
 			goto out;
 	} else {
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -199,9 +199,7 @@ static int setfl(int fd, struct file * f
 static void f_modown(struct file *filp, struct pid *pid, enum pid_type type,
                      int force)
 {
-	unsigned long flags;
-
-	write_lock_irqsave(&filp->f_owner.lock, flags);
+	write_lock_irq(&filp->f_owner.lock);
 	if (force || !filp->f_owner.pid) {
 		put_pid(filp->f_owner.pid);
 		filp->f_owner.pid = get_pid(pid);
@@ -213,7 +211,7 @@ static void f_modown(struct file *filp,
 			filp->f_owner.euid = cred->euid;
 		}
 	}
-	write_unlock_irqrestore(&filp->f_owner.lock, flags);
+	write_unlock_irq(&filp->f_owner.lock);
 }
 
 int __f_setown(struct file *filp, struct pid *pid, enum pid_type type,


Index: kernel.spec
===================================================================
RCS file: /cvs/pkgs/rpms/kernel/F-12/kernel.spec,v
retrieving revision 1.2017
retrieving revision 1.2018
diff -u -p -r1.2017 -r1.2018
--- kernel.spec	17 Feb 2010 17:51:00 -0000	1.2017
+++ kernel.spec	17 Feb 2010 18:16:22 -0000	1.2018
@@ -769,6 +769,7 @@ Patch12319: vgaarb-fix-userspace-ptr-der
 # cve-2009-4537
 Patch12320: linux-2.6-net-r8169-improved-rx-length-check-errors.patch
 
+Patch12330: fix-race-in-tty_fasync-properly.patch
 # ==============================================================================
 
 %endif
@@ -1413,6 +1414,8 @@ ApplyPatch vgaarb-fix-userspace-ptr-dere
 # cve-2009-4537
 ApplyPatch linux-2.6-net-r8169-improved-rx-length-check-errors.patch
 
+ApplyPatch fix-race-in-tty_fasync-properly.patch
+
 # END OF PATCH APPLICATIONS ====================================================
 
 %endif
@@ -2068,6 +2071,10 @@ fi
 # and build.
 
 %changelog
+* Wed Feb 17 2010 Chuck Ebbert <cebbert at redhat.com>  2.6.32.8-58
+- fix-race-in-tty_fasync-properly.patch: fix for deadlock caused
+  by original patch in 2.6.32.6 
+
 * Wed Feb 17 2010 Chuck Ebbert <cebbert at redhat.com>  2.6.32.8-57
 - CVE-2010-0623 kernel: local DoS via futex_lock_pi