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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>
This commit is contained in:
Mathias Nyman 2017-01-03 18:28:48 +02:00 committed by Greg Kroah-Hartman
parent 2a7cfdf37b
commit a5a1b95141
1 changed files with 5 additions and 1 deletions
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6
drivers/usb/host/xhci-ring.c
View File

@ -1269,7 +1269,11 @@ void xhci_handle_command_timeout(unsigned long data)
spin_lock_irqsave(&xhci->lock, flags); 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); spin_unlock_irqrestore(&xhci->lock, flags);
return; return;
} }