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authorMathias Nyman <mathias.nyman@linux.intel.com>2017-01-03 18:28:48 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-03 17:37:32 +0100
commita5a1b9514154437aa1ed35c291191f82fd3e941a (patch)
treed166091e509be9a6b07ed40103deb29c797afbb4 /drivers/usb
parent2a7cfdf37b7c08ac29df4c62ea5ccb01474b6597 (diff)
xhci: Handle command completion and timeout race
If we get a command completion event at the same time as the command timeout work starts on another cpu we might end up aborting the wrong command. If the command completion takes the xhci lock before the timeout work, it will handle the command, pick the next command, mark it as current_cmd, and re-queue the timeout work. When the timeout work finally gets the lock It will start aborting the wrong command. This case can be resolved by checking if the timeout work is pending inside the timeout function itself. A new timeout work can only be pending if the command completed and a new command was queued. If there are no more commands pending then command completion will set the current_cmd to NULL, which is already handled in the timeout work. Cc: <stable@vger.kernel.org> Reported-by: Baolin Wang <baolin.wang@linaro.org> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/host/xhci-ring.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index bc8be6f6669e..935193c6bf23 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1269,7 +1269,11 @@ void xhci_handle_command_timeout(unsigned long data)
spin_lock_irqsave(&xhci->lock, flags);
- if (!xhci->current_cmd) {
+ /*
+ * If timeout work is pending, or current_cmd is NULL, it means we
+ * raced with command completion. Command is handled so just return.
+ */
+ if (!xhci->current_cmd || timer_pending(&xhci->cmd_timer)) {
spin_unlock_irqrestore(&xhci->lock, flags);
return;
}