Hi Dean,
* dean_jenkins@xxxxxxxxxx <dean_jenkins@xxxxxxxxxx> [2013-02-25 16:38:33 +0000]:
> From: Dean Jenkins <Dean_Jenkins@xxxxxxxxxx>
>
> A race condition exists between near simultaneous asynchronous
> DLC data channel disconnection requests from the host and remote device.
> This causes the socket layer to request a socket shutdown at the same
> time the rfcomm core is processing the disconnect request from the remote
> device.
>
> The socket layer retains a copy of a struct rfcomm_dlc d pointer.
> The d pointer refers to a copy of a struct rfcomm_session.
> When the socket layer thread performs a socket shutdown, the thread
> may wait on a rfcomm lock in rfcomm_dlc_close(). This means that
> whilst the thread waits, the rfcomm_session and/or rfcomm_dlc structures
> pointed to by d maybe freed due to rfcomm core handling. Consequently,
> when the rfcomm lock becomes available and the thread runs, a
> malfunction could occur as a freed rfcomm_session structure and/or a
> freed rfcomm_dlc structure will be erroneously accessed.
>
> Therefore, after the rfcomm lock is acquired, check that the struct
> rfcomm_session is still valid by searching the rfcomm session list.
> If the session is valid then validate the d pointer by searching the
> rfcomm session list of active DLCs for the rfcomm_dlc structure
> pointed by d.
>
> Signed-off-by: Dean Jenkins <Dean_Jenkins@xxxxxxxxxx>
> ---
> net/bluetooth/rfcomm/core.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
> index 8780e67..af0c26d 100644
> --- a/net/bluetooth/rfcomm/core.c
> +++ b/net/bluetooth/rfcomm/core.c
> @@ -493,12 +493,34 @@ static int __rfcomm_dlc_close(struct rfcomm_dlc *d, int err)
>
> int rfcomm_dlc_close(struct rfcomm_dlc *d, int err)
> {
> - int r;
> + int r = 0;
> + struct rfcomm_dlc *d_list;
> + struct rfcomm_session *s, *s_list;
> +
> + BT_DBG("dlc %p state %ld dlci %d err %d", d, d->state, d->dlci, err);
>
> rfcomm_lock();
>
> - r = __rfcomm_dlc_close(d, err);
> + s = d->session;
> + if (!s)
> + goto no_session;
> +
> + /* after waiting on the mutex check the session still exists */
> + list_for_each_entry(s_list, &session_list, list) {
> + if (s_list == s) {
> + /* after waiting on the mutex, */
> + /* check the dlc still exists */
Just a very small issue, this comment here is not following our coding style.
If you want a multiple line comment do something like this:
/* after waiting on the mutex,
* check the dlc still exists
*/
But I will just recommend you merge this comment with the one before the first
list_for_each_entry. please send an updated version of this patch so I can go
ahead and apply it.
Gustavo
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