From: Lu Baolu <baolu.lu@linux.intel.com>
To: Baolin Wang <baolin.wang@linaro.org>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>,
USB <linux-usb@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/1] usb: xhci: fix possible wild pointer
Date: Fri, 2 Dec 2016 12:40:37 +0800 [thread overview]
Message-ID: <5840FB45.60302@linux.intel.com> (raw)
In-Reply-To: <CAMz4ku+5GUJ9zgbn6Eb3uf_+TaMCBd1iHH5T-GWNycYt58_mXw@mail.gmail.com>
Hi,
On 12/02/2016 12:18 PM, Baolin Wang wrote:
> On 2 December 2016 at 10:29, Lu Baolu <baolu.lu@linux.intel.com> wrote:
>> 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@vger.kernel.org> # v3.16+
>> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Nice catch. I was also curious where set xhci->current_cmd to be NULL
> when current command is freed.
Below code does:
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");
}
Best regards,
Lu Baolu
> Tested-by: Baolin Wang <baolin.wang@linaro.org>
>
>> ---
>> 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
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-usb" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
next prev parent reply other threads:[~2016-12-02 4:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-02 2:29 [PATCH 1/1] usb: xhci: fix possible wild pointer Lu Baolu
2016-12-02 4:18 ` Baolin Wang
2016-12-02 4:40 ` Lu Baolu [this message]
2016-12-02 4:48 ` Baolin Wang
2016-12-02 13:39 ` Mathias Nyman
2016-12-05 9:07 ` Lu Baolu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5840FB45.60302@linux.intel.com \
--to=baolu.lu@linux.intel.com \
--cc=baolin.wang@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=mathias.nyman@linux.intel.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).