6.17-stable review patch. If anyone has any objections, please let me know.
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From: Duoming Zhou duoming@zju.edu.cn
commit 67600ccfc4f38ebd331b9332ac94717bfbc87ea7 upstream.
The original code relies on cancel_delayed_work() in tb_dp_dprx_stop(), which does not ensure that the delayed work item tunnel->dprx_work has fully completed if it was already running. This leads to use-after-free scenarios where tb_tunnel is deallocated by tb_tunnel_put(), while tunnel->dprx_work remains active and attempts to dereference tb_tunnel in tb_dp_dprx_work().
A typical race condition is illustrated below:
CPU 0 | CPU 1 tb_dp_tunnel_active() | tb_deactivate_and_free_tunnel()| tb_dp_dprx_start() tb_tunnel_deactivate() | queue_delayed_work() tb_dp_activate() | tb_dp_dprx_stop() | tb_dp_dprx_work() //delayed worker cancel_delayed_work() | tb_tunnel_put(tunnel); | | tunnel = container_of(...); //UAF | tunnel-> //UAF
Replacing cancel_delayed_work() with cancel_delayed_work_sync() is not feasible as it would introduce a deadlock: both tb_dp_dprx_work() and the cleanup path acquire tb->lock, and cancel_delayed_work_sync() would wait indefinitely for the work item that cannot proceed.
Instead, implement proper reference counting: - If cancel_delayed_work() returns true (work is pending), we release the reference in the stop function. - If it returns false (work is executing or already completed), the reference is released in delayed work function itself.
This ensures the tb_tunnel remains valid during work item execution while preventing memory leaks.
This bug was found by static analysis.
Fixes: d6d458d42e1e ("thunderbolt: Handle DisplayPort tunnel activation asynchronously") Cc: stable@vger.kernel.org Signed-off-by: Duoming Zhou duoming@zju.edu.cn Signed-off-by: Mika Westerberg mika.westerberg@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/thunderbolt/tunnel.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/thunderbolt/tunnel.c +++ b/drivers/thunderbolt/tunnel.c @@ -1073,6 +1073,7 @@ static void tb_dp_dprx_work(struct work_
if (tunnel->callback) tunnel->callback(tunnel, tunnel->callback_data); + tb_tunnel_put(tunnel); }
static int tb_dp_dprx_start(struct tb_tunnel *tunnel) @@ -1100,8 +1101,8 @@ static void tb_dp_dprx_stop(struct tb_tu if (tunnel->dprx_started) { tunnel->dprx_started = false; tunnel->dprx_canceled = true; - cancel_delayed_work(&tunnel->dprx_work); - tb_tunnel_put(tunnel); + if (cancel_delayed_work(&tunnel->dprx_work)) + tb_tunnel_put(tunnel); } }