From 3a24934f065d23145f1c9c70da9f630c7a37795f Mon Sep 17 00:00:00 2001
From: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
Date: Thu, 20 May 2010 12:27:58 -0700
Subject: [PATCH] wimax/i2400m: fix bad race condition check in RX path
The i2400m->rx_roq data structure is protected against race conditions
with a reference count (i2400m->rx_roq_refcount); the pointer can be
read-referenced under the i2400m->rx_lock spinlock.
The code in i2400m_rx_edata() wasn't properly following access
protocol, performing an invalid check on i2400m->rx_roq (which is
cleared to NULL when the refcount drops to zero). As such, it was
missing to detect when the data structure is no longer valid and
oopsing with a NULL pointer dereference.
This commit fixes said check by verifying, under the rx_lock spinlock,
that i2400m->rx_roq is non-NULL and then increasing the reference
count before dropping the spinlock.
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
---
drivers/net/wimax/i2400m/rx.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/wimax/i2400m/rx.c b/drivers/net/wimax/i2400m/rx.c
index c835ae8b89ce..6cd12d64fc7a 100644
--- a/drivers/net/wimax/i2400m/rx.c
+++ b/drivers/net/wimax/i2400m/rx.c
@@ -1033,12 +1033,12 @@ void i2400m_rx_edata(struct i2400m *i2400m, struct sk_buff *skb_rx,
ro_sn = (reorder >> I2400M_RO_SN_SHIFT) & I2400M_RO_SN;
spin_lock_irqsave(&i2400m->rx_lock, flags);
- roq = &i2400m->rx_roq[ro_cin];
- if (roq == NULL) {
+ if (i2400m->rx_roq == NULL) {
kfree_skb(skb); /* rx_roq is already destroyed */
spin_unlock_irqrestore(&i2400m->rx_lock, flags);
goto error;
}
+ roq = &i2400m->rx_roq[ro_cin];
kref_get(&i2400m->rx_roq_refcount);
spin_unlock_irqrestore(&i2400m->rx_lock, flags);