scsi: imm: Fix use-after-free bug caused by unfinished delayed work

The delayed work item 'imm_tq' is initialized in imm_attach() and
scheduled via imm_queuecommand() for processing SCSI commands.  When the
IMM parallel port SCSI host adapter is detached through imm_detach(),
the imm_struct device instance is deallocated.

However, the delayed work might still be pending or executing
when imm_detach() is called, leading to use-after-free bugs
when the work function imm_interrupt() accesses the already
freed imm_struct memory.

The race condition can occur as follows:

CPU 0(detach thread)   | CPU 1
                       | imm_queuecommand()
                       |   imm_queuecommand_lck()
imm_detach()           |     schedule_delayed_work()
  kfree(dev) //FREE    | imm_interrupt()
                       |   dev = container_of(...) //USE
                           dev-> //USE

Add disable_delayed_work_sync() in imm_detach() to guarantee proper
cancellation of the delayed work item before imm_struct is deallocated.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://patch.msgid.link/20251028100149.40721-1-duoming@zju.edu.cn
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/imm.c b/drivers/scsi/imm.c
index 5c602c0577989fe179b2e19cf3c8a8c8d25f8010..45b0e33293a5917112987807a7a02df73b1ee39e 100644 (file)
--- a/drivers/scsi/imm.c
+++ b/drivers/scsi/imm.c
@@ -1260,6 +1260,7 @@ static void imm_detach(struct parport *pb)
        imm_struct *dev;
        list_for_each_entry(dev, &imm_hosts, list) {
                if (dev->dev->port == pb) {
+                       disable_delayed_work_sync(&dev->imm_tq);
                        list_del_init(&dev->list);
                        scsi_remove_host(dev->host);
                        scsi_host_put(dev->host);