This is a note to let you know that I've just added the patch titled
usb: xhci: fix possible wild pointer
to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 2b985467371a58ae44d76c7ba12b0951fee6ed98 Mon Sep 17 00:00:00 2001
From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Date: Tue, 3 Jan 2017 18:28:46 +0200
Subject: usb: xhci: fix possible wild pointer
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>
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(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index bdf6b13d9b67..acc37311c938 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1267,14 +1267,18 @@ 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;
}
+ /* 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) &&
@@ -1422,6 +1426,8 @@ 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;
}
event_handled:
--
2.11.0
--
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