ptp: ocp: fix use-after-free bugs causing by ptp_ocp_watchdog

The ptp_ocp_detach() only shuts down the watchdog timer if it is
pending. However, if the timer handler is already running, the
timer_delete_sync() is not called. This leads to race conditions
where the devlink that contains the ptp_ocp is deallocated while
the timer handler is still accessing it, resulting in use-after-free
bugs. The following details one of the race scenarios.

(thread 1)                           | (thread 2)
ptp_ocp_remove()                     |
  ptp_ocp_detach()                   | ptp_ocp_watchdog()
    if (timer_pending(&bp->watchdog))|   bp = timer_container_of()
      timer_delete_sync()            |
                                     |
  devlink_free(devlink) //free       |
                                     |   bp-> //use

Resolve this by unconditionally calling timer_delete_sync() to ensure
the timer is reliably deactivated, preventing any access after free.

Fixes: 773bda964921 ("ptp: ocp: Expose various resources on the timecard.")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250828082949.28189-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
index d39073dc4072d2deea2c93c79f2c69ae3bad78d2..4e1286ce05c9afa08fb1d4f8b23d76d1e5e412b4 100644 (file)
--- a/drivers/ptp/ptp_ocp.c
+++ b/drivers/ptp/ptp_ocp.c
@@ -4557,8 +4557,7 @@ ptp_ocp_detach(struct ptp_ocp *bp)
        ptp_ocp_debugfs_remove_device(bp);
        ptp_ocp_detach_sysfs(bp);
        ptp_ocp_attr_group_del(bp);
-       if (timer_pending(&bp->watchdog))
-               timer_delete_sync(&bp->watchdog);
+       timer_delete_sync(&bp->watchdog);
        if (bp->ts0)
                ptp_ocp_unregister_ext(bp->ts0);
        if (bp->ts1)