summaryrefslogtreecommitdiff
path: root/drivers/net/netconsole.c
diff options
context:
space:
mode:
authorNikolay Aleksandrov <nikolay@redhat.com>2013-10-23 17:04:49 +0400
committerDavid S. Miller <davem@davemloft.net>2013-10-26 03:26:58 +0400
commit45e526e80e6fdc796d3bc05716d5c930a427df4d (patch)
tree1d6909c66190e5e5a30c28fa66b6edd760126f07 /drivers/net/netconsole.c
parent0e67d9903d71ce3c5889fa2e1788d4335794a0f6 (diff)
downloadlinux-45e526e80e6fdc796d3bc05716d5c930a427df4d.tar.xz
netconsole: fix NULL pointer dereference
We need to disable the netconsole (enabled = 0) before setting nt->np.dev to NULL because otherwise we might still have users after the netpoll_cleanup() since nt->enabled is set afterwards and we can have a message which will result in a NULL pointer dereference. It is very easy to hit dereferences all over the netpoll_send_udp function by running the following two loops in parallel: while [ 1 ]; do echo 1 > enabled; echo 0 > enabled; done; while [ 1 ]; do echo 00:11:22:33:44:55 > remote_mac; done; (the second loop is to generate messages, it can be done by anything) We're safe to set nt->np.dev = NULL and nt->enabled = 0 with the spinlock since it's required in the write_msg() function. Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com> Reviewed-by: Veacelsav Falico <vfalico@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/netconsole.c')
-rw-r--r--drivers/net/netconsole.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index adeee615dd19..1505dcb950fa 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -310,6 +310,7 @@ static ssize_t store_enabled(struct netconsole_target *nt,
const char *buf,
size_t count)
{
+ unsigned long flags;
int enabled;
int err;
@@ -342,6 +343,13 @@ static ssize_t store_enabled(struct netconsole_target *nt,
printk(KERN_INFO "netconsole: network logging started\n");
} else { /* 0 */
+ /* We need to disable the netconsole before cleaning it up
+ * otherwise we might end up in write_msg() with
+ * nt->np.dev == NULL and nt->enabled == 1
+ */
+ spin_lock_irqsave(&target_list_lock, flags);
+ nt->enabled = 0;
+ spin_unlock_irqrestore(&target_list_lock, flags);
netpoll_cleanup(&nt->np);
}