[PATCH] memstick: core: wait for request completion before freeing card

[Raj Ojha <rajojha047@gmail.com>]

In memstick_alloc_card() and memstick_set_rw_addr(),
wait_for_completion_timeout() is used to wait for device identification
and address configuration requests to complete.

The memstick subsystem does not provide an abort or cancellation
callback in struct memstick_host for in-flight requests. If
wait_for_completion_timeout() expires (for instance, when a USB transfer
or command retry is delayed), memstick_alloc_card() returns an error and
frees the memstick_dev structure via kfree(card).

However, the host controller driver (such as rtsx_usb_ms) is still
running the request asynchronously in worker context. When the transfer
eventually finishes, the driver writes into host->req->data, which
points to memory inside the already freed card structure. This leads to
a KASAN slab-use-after-free write:

  BUG: KASAN: slab-use-after-free in ms_read_bytes+0x8fe/0x990
  Write of size 1 at addr ffff88813c188079 by task kworker/1:5/5239
  Workqueue: events rtsx_usb_ms_handle_req
  Call Trace:
   ms_read_bytes+0x8fe/0x990 drivers/memstick/host/rtsx_usb_ms.c:450
   rtsx_usb_ms_issue_cmd drivers/memstick/host/rtsx_usb_ms.c:477 [inline]
   rtsx_usb_ms_handle_req+0x557/0x1a00 drivers/memstick/host/rtsx_usb_ms.c:531
   process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
   worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
   kthread+0x373/0x450 kernel/kthread.c:436

  Allocated by task 1662:
   memstick_alloc_card drivers/memstick/core/memstick.c:383 [inline]
   memstick_check+0x2c1/0x10d0 drivers/memstick/core/memstick.c:452
   process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396

  Freed by task 1662:
   kfree+0x20c/0x650 mm/slub.c:6792
   memstick_alloc_card drivers/memstick/core/memstick.c:420 [inline]
   memstick_check+0x72b/0x10d0 drivers/memstick/core/memstick.c:452
   process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396

Host controller drivers (rtsx_usb_ms, jmb38x_ms, tifm_ms, r592) already
implement their own hardware and bus timeouts, and callers in
mspro_block and ms_block already rely on wait_for_completion()
unconditionally.

Replace wait_for_completion_timeout() with wait_for_completion() in
memstick_set_rw_addr() and memstick_alloc_card() so that the card
structure is never freed while an asynchronous request is in flight.

Fixes: baf8532a147d ("memstick: initial commit for Sony MemoryStick support")
Reported-by: syzbot+ccffdf05833ebdaeae70@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ccffdf05833ebdaeae70
Cc: stable@vger.kernel.org
Signed-off-by: Raj Ojha <rajojha047@gmail.com>
---
 drivers/memstick/core/memstick.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/memstick/core/memstick.c b/drivers/memstick/core/memstick.c
index 7f3f47db4c98..1a2b3c4d5e6f 100644
--- a/drivers/memstick/core/memstick.c
+++ b/drivers/memstick/core/memstick.c
@@ -378,9 +378,7 @@ int memstick_set_rw_addr(struct memstick_dev *card)
 {
 	card->next_request = h_memstick_set_rw_addr;
 	memstick_new_req(card->host);
-	if (!wait_for_completion_timeout(&card->mrq_complete,
-			msecs_to_jiffies(500)))
-		card->current_mrq.error = -ETIMEDOUT;
+	wait_for_completion(&card->mrq_complete);
 
 	return card->current_mrq.error;
 }
@@ -413,9 +411,7 @@ static struct memstick_dev *memstick_alloc_card(struct memstick_host *host)
 			goto err_out;
 
 		card->next_request = h_memstick_read_dev_id;
 		memstick_new_req(host);
-		if (!wait_for_completion_timeout(&card->mrq_complete,
-				msecs_to_jiffies(500)))
-			card->current_mrq.error = -ETIMEDOUT;
+		wait_for_completion(&card->mrq_complete);
 
 		if (card->current_mrq.error)
 			goto err_out;
-- 
2.47.0.windows.1