4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
commit 2b985467371a58ae44d76c7ba12b0951fee6ed98 upstream.
handle_cmd_completion() frees a command structure which might be still
referenced by xhci->current_cmd.
This might cause problem when xhci->current_cmd is accessed after that.
A real-life case could be like this. The host takes a very long time to
respond to a command, and the command timer is fired at the same time
when the command completion event arrives. The command completion
handler frees xhci->current_cmd before the timer function can grab
xhci->lock. Afterward, timer function grabs the lock and go ahead with
checking and setting members of xhci->current_cmd.
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci-ring.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1268,14 +1268,18 @@ void xhci_handle_command_timeout(unsigne
bool second_timeout = false;
xhci = (struct xhci_hcd *) data;
- /* mark this command to be cancelled */
spin_lock_irqsave(&xhci->lock, flags);
- if (xhci->current_cmd) {
- if (xhci->current_cmd->status == COMP_CMD_ABORT)
- second_timeout = true;
- xhci->current_cmd->status = COMP_CMD_ABORT;
+
+ if (!xhci->current_cmd) {
+ spin_unlock_irqrestore(&xhci->lock, flags);
+ return;
}
+ /* mark this command to be cancelled */
+ if (xhci->current_cmd->status == COMP_CMD_ABORT)
+ second_timeout = true;
+ xhci->current_cmd->status = COMP_CMD_ABORT;
+
/* Make sure command ring is running before aborting it */
hw_ring_state = xhci_read_64(xhci, &xhci->op_regs->cmd_ring);
if ((xhci->cmd_ring_state & CMD_RING_STATE_RUNNING) &&
@@ -1424,6 +1428,8 @@ static void handle_cmd_completion(struct
xhci->current_cmd = list_entry(cmd->cmd_list.next,
struct xhci_command, cmd_list);
mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
+ } else if (xhci->current_cmd == cmd) {
+ xhci->current_cmd = NULL;
}
event_handled:
--
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