[PATCH 1/2] wifi: mwifiex: Detach sync cmd buffer on interrupted wait

[Fabio Estevam <festevam@gmail.com>]

From: Fabio Estevam <festevam@nabladev.com>

mwifiex synchronous commands keep the caller-provided data buffer in
cmd_node->data_buf. Several callers pass stack-allocated objects there.

If wait_event_interruptible_timeout() is interrupted, the caller can
return and release that stack object while the firmware command is still
the current command. A late firmware response then reaches the normal
response handler, which can copy data through cmd_node->data_buf into the
stale stack address.

This fixes a stack corruption observed during repeated association and
disassociation cycles. The panic trace showed the command wait being
interrupted immediately before a bad pointer dereference:

  cmd_wait_q terminated: -512
  Unable to handle kernel paging request at virtual address 002c583837384662
  Kernel panic - not syncing: stack-protector: Kernel stack is corrupted
  ...
  Tainted: [M]=MACHINE_CHECK

The fault address decodes as little-endian ASCII:

  0x002c583837384662 -> "bF878X,\0"

which is a fragment of the VERSION_EXT firmware string exposed as
debugfs "verext":

  w8997o-V4, RF878X, FP92, 16.92.21.p153.7

The same runs also showed corrupted control data containing:

  0x2400372e333531 -> "153.7\0$"

which is the tail of the same VERSION_EXT string. This points at a late
VERSION_EXT response writing through a stale stack-backed data_buf after
the interrupted wait returned.

After cancelling pending commands on an interrupted or timed-out wait,
detach the caller-owned data buffer from the still-current command. This
preserves the existing command cancellation behaviour while preventing a
late response from writing through a pointer whose lifetime ended with the
waiting caller.

Tested on an i.MX8MP board using an 88W8997.

Cc: stable@vger.kernel.org
Fixes: 3d026d09b28d ("mwifiex: cancel pending commands for signal")
Signed-off-by: Fabio Estevam <festevam@nabladev.com>
---
 drivers/net/wireless/marvell/mwifiex/sta_ioctl.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/wireless/marvell/mwifiex/sta_ioctl.c b/drivers/net/wireless/marvell/mwifiex/sta_ioctl.c
index 9460d5352b23..19196848778c 100644
--- a/drivers/net/wireless/marvell/mwifiex/sta_ioctl.c
+++ b/drivers/net/wireless/marvell/mwifiex/sta_ioctl.c
@@ -57,6 +57,18 @@ int mwifiex_wait_queue_complete(struct mwifiex_adapter *adapter,
 		mwifiex_dbg(adapter, ERROR, "cmd_wait_q terminated: %d\n",
 			    status);
 		mwifiex_cancel_all_pending_cmd(adapter);
+
+		/* The command response path writes through cmd_node->data_buf.
+		 * On an interrupted wait, the caller can return and release a
+		 * stack-allocated data_buf before a late firmware response is
+		 * processed. Detach the caller-owned buffer from the current
+		 * command so a late response cannot corrupt freed stack memory.
+		 */
+		spin_lock_bh(&adapter->mwifiex_cmd_lock);
+		if (adapter->curr_cmd == cmd_queued)
+			adapter->curr_cmd->data_buf = NULL;
+		spin_unlock_bh(&adapter->mwifiex_cmd_lock);
+
 		return status;
 	}
 
-- 
2.43.0