n_gsm: avoid accessing freed memory during CMD_FCOFF condition
gsm_data_kick was recently modified to allow messages on the
tx queue bound for DLCI0 to flow even during FCOFF conditions.
Unfortunately we introduced a bug discovered by code inspection
where subsequent list traversers can access freed memory if
the DLCI0 messages were not all at the head of the list.
Replaced singly linked tx list w/ a list_head and used
provided interfaces for traversing and deleting members.
Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Tested-by: Yin, Fengwei <fengwei.yin@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Riding School <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 0d93e51..6f4f8d3 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -108,7 +108,7 @@
*/
struct gsm_msg {
- struct gsm_msg *next;
+ struct list_head list;
u8 addr; /* DLCI address + flags */
u8 ctrl; /* Control byte + flags */
unsigned int len; /* Length of data block (can be zero) */
@@ -245,8 +245,7 @@
unsigned int tx_bytes; /* TX data outstanding */
#define TX_THRESH_HI 8192
#define TX_THRESH_LO 2048
- struct gsm_msg *tx_head; /* Pending data packets */
- struct gsm_msg *tx_tail;
+ struct list_head tx_list; /* Pending data packets */
/* Control messages */
struct timer_list t2_timer; /* Retransmit timer for commands */
@@ -663,7 +662,7 @@
m->len = len;
m->addr = addr;
m->ctrl = ctrl;
- m->next = NULL;
+ INIT_LIST_HEAD(&m->list);
return m;
}
@@ -681,16 +680,13 @@
static void gsm_data_kick(struct gsm_mux *gsm)
{
- struct gsm_msg *msg = gsm->tx_head;
- struct gsm_msg *free_msg;
+ struct gsm_msg *msg, *nmsg;
int len;
int skip_sof = 0;
- while (msg) {
- if (gsm->constipated && msg->addr) {
- msg = msg->next;
+ list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) {
+ if (gsm->constipated && msg->addr)
continue;
- }
if (gsm->encoding != 0) {
gsm->txframe[0] = GSM1_SOF;
len = gsm_stuff_frame(msg->data,
@@ -718,14 +714,9 @@
burst */
skip_sof = 1;
- if (gsm->tx_head == msg)
- gsm->tx_head = msg->next;
- free_msg = msg;
- msg = msg->next;
- kfree(free_msg);
+ list_del(&msg->list);
+ kfree(msg);
}
- if (!gsm->tx_head)
- gsm->tx_tail = NULL;
}
/**
@@ -774,11 +765,7 @@
msg->data = dp;
/* Add to the actual output queue */
- if (gsm->tx_tail)
- gsm->tx_tail->next = msg;
- else
- gsm->tx_head = msg;
- gsm->tx_tail = msg;
+ list_add_tail(&msg->list, &gsm->tx_list);
gsm->tx_bytes += msg->len;
gsm_data_kick(gsm);
}
@@ -2026,7 +2013,7 @@
{
int i;
struct gsm_dlci *dlci = gsm->dlci[0];
- struct gsm_msg *txq;
+ struct gsm_msg *txq, *utxq;
struct gsm_control *gc;
gsm->dead = 1;
@@ -2061,11 +2048,9 @@
if (gsm->dlci[i])
gsm_dlci_release(gsm->dlci[i]);
/* Now wipe the queues */
- for (txq = gsm->tx_head; txq != NULL; txq = gsm->tx_head) {
- gsm->tx_head = txq->next;
+ list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list)
kfree(txq);
- }
- gsm->tx_tail = NULL;
+ INIT_LIST_HEAD(&gsm->tx_list);
}
EXPORT_SYMBOL_GPL(gsm_cleanup_mux);
@@ -2176,6 +2161,7 @@
}
spin_lock_init(&gsm->lock);
kref_init(&gsm->ref);
+ INIT_LIST_HEAD(&gsm->tx_list);
gsm->t1 = T1;
gsm->t2 = T2;