linux-kernel - [PATCH] firewire: fill_bus_reset

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 6 Jun 2008 22:11:30 +0200 (CEST)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] firewire: fill_bus_reset_event needs lock protection

Callers of fill_bus_reset_event() have to take card->lock.  Otherwise
access to node data may oops if node removal is in progress.

A lockless alternative would be

-	event->local_node_id = card->local_node->node_id;
+	tmp = fw_node_get(card->local_node);
+	event->local_node_id = tmp->node_id;
+	fw_node_put(tmp);

and ditto with the other node pointers which fill_bus_reset_event()
accesses.  But I went the locked route because one of the two callers
already holds the lock.  As a bonus, we don't need the memory barrier
anymore because device->generation and device->node_id are written in
a card->lock protected section.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/fw-cdev.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Index: linux/drivers/firewire/fw-cdev.c
===================================================================
--- linux.orig/drivers/firewire/fw-cdev.c
+++ linux/drivers/firewire/fw-cdev.c
@@ -205,6 +205,7 @@ fw_device_op_read(struct file *file,
 	return dequeue_event(client, buffer, count);
 }
 
+/* caller must hold card->lock so that node pointers can be dereferenced here */
 static void
 fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
 		     struct client *client)
@@ -214,7 +215,6 @@ fill_bus_reset_event(struct fw_cdev_even
 	event->closure	     = client->bus_reset_closure;
 	event->type          = FW_CDEV_EVENT_BUS_RESET;
 	event->generation    = client->device->generation;
-	smp_rmb();           /* node_id must not be older than generation */
 	event->node_id       = client->device->node_id;
 	event->local_node_id = card->local_node->node_id;
 	event->bm_node_id    = 0; /* FIXME: We don't track the BM. */
@@ -274,6 +274,7 @@ static int ioctl_get_info(struct client 
 {
 	struct fw_cdev_get_info *get_info = buffer;
 	struct fw_cdev_event_bus_reset bus_reset;
+	struct fw_card *card = client->device->card;
 	unsigned long ret = 0;
 
 	client->version = get_info->version;
@@ -299,13 +300,17 @@ static int ioctl_get_info(struct client 
 	client->bus_reset_closure = get_info->bus_reset_closure;
 	if (get_info->bus_reset != 0) {
 		void __user *uptr = u64_to_uptr(get_info->bus_reset);
+		unsigned long flags;
 
+		spin_lock_irqsave(&card->lock, flags);
 		fill_bus_reset_event(&bus_reset, client);
+		spin_unlock_irqrestore(&card->lock, flags);
+
 		if (copy_to_user(uptr, &bus_reset, sizeof(bus_reset)))
 			return -EFAULT;
 	}
 
-	get_info->card = client->device->card->index;
+	get_info->card = card->index;
 
 	return 0;
 }

-- 
Stefan Richter
-=====-==--- -==- --==-
http://arcgraph.de/sr/

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/