ACPI / IPMI: Fix race caused by the unprotected ACPI IPMI transfers

This patch fixes races caused by unprotected ACPI IPMI transfers.

We can see that the following crashes may occur:
 1. There is no tx_msg_lock held for iterating tx_msg_list in
    ipmi_flush_tx_msg() while it may be unlinked on failure in
    parallel in acpi_ipmi_space_handler() under tx_msg_lock.
 2. There is no lock held for freeing tx_msg in acpi_ipmi_space_handler()
    while it may be accessed in parallel in ipmi_flush_tx_msg() and
    ipmi_msg_handler().

This patch enhances tx_msg_lock to protect all tx_msg accesses to solve
this issue.  Then tx_msg_lock is always held around complete() and tx_msg
accesses.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Reviewed-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
index 7397135702db..87307baeafab 100644
--- a/drivers/acpi/acpi_ipmi.c
+++ b/drivers/acpi/acpi_ipmi.c
@@ -228,11 +228,14 @@ static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
         struct acpi_ipmi_msg *tx_msg, *temp;
         int count = HZ / 10;
         struct pnp_dev *pnp_dev = ipmi->pnp_dev;
+        unsigned long flags;
 
+        spin_lock_irqsave(&ipmi->tx_msg_lock, flags);
         list_for_each_entry_safe(tx_msg, temp, &ipmi->tx_msg_list, head) {
                 /* wake up the sleep thread on the Tx msg */
                 complete(&tx_msg->tx_complete);
         }
+        spin_unlock_irqrestore(&ipmi->tx_msg_lock, flags);
 
         /* wait for about 100ms to flush the tx message list */
         while (count--) {
@@ -266,11 +269,10 @@ static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
                 }
         }
 
-        spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
         if (!msg_found) {
                 dev_warn(&pnp_dev->dev, "Unexpected response (msg id %ld) is "
                         "returned.\n", msg->msgid);
-                goto out_msg;
+                goto out_lock;
         }
 
         /* copy the response data to Rx_data buffer */
@@ -284,6 +286,8 @@ static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
                 tx_msg->msg_done = 1;
         }
         complete(&tx_msg->tx_complete);
+out_lock:
+        spin_unlock_irqrestore(&ipmi_device->tx_msg_lock, flags);
 out_msg:
         ipmi_free_recv_msg(msg);
 };