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.
Cc: <stable@xxxxxxxxxxxxxxx> # v3.16+
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
drivers/usb/host/xhci-ring.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index bdf6b13..13e05f6 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1267,14 +1267,16 @@ void xhci_handle_command_timeout(unsigned long data)
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;
}
+ 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) &&
@@ -1422,6 +1424,10 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
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;
+ } else {
+ xhci_warn(xhci, "WARN current_cmd doesn't match command\n");
}
event_handled:
--
2.1.4
--
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