+ rapidio-mport_cdev-fix-use-after-free-in-dma_req_free.patch added to mm-nonmm-unstable branch

+ rapidio-mport_cdev-fix-use-after-free-in-dma_req_free.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: rapidio: mport_cdev: fix use-after-free in dma_req_free()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     rapidio-mport_cdev-fix-use-after-free-in-dma_req_free.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/rapidio-mport_cdev-fix-use-after-free-in-dma_req_free.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: James Kim <james010kim@gmail.com>
Subject: rapidio: mport_cdev: fix use-after-free in dma_req_free()
Date: Mon, 15 Jun 2026 16:05:30 +0900

dma_req_free() drops the mapping reference under buf_mutex and then
dereferences req->map again to unlock the mutex.

If kref_put() drops the last reference, mport_release_mapping() frees the
mapping, and the subsequent mutex_unlock() dereferences a freed object. 
This is a use-after-free.

Fix this by caching map and md before kref_put() and using the cached md
for mutex unlocking.

Link: https://lore.kernel.org/20260615070530.371640-1-james010kim@gmail.com
Fixes: e8de370188d0 ("rapidio: add mport char device driver")
Signed-off-by: James Kim <james010kim@gmail.com>
Cc: Alexandre Bounine <alex.bou9@gmail.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/rapidio/devices/rio_mport_cdev.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/rapidio/devices/rio_mport_cdev.c~rapidio-mport_cdev-fix-use-after-free-in-dma_req_free
+++ a/drivers/rapidio/devices/rio_mport_cdev.c
@@ -564,9 +564,14 @@ static void dma_req_free(struct kref *re
 	}
 
 	if (req->map) {
-		mutex_lock(&req->map->md->buf_mutex);
-		kref_put(&req->map->ref, mport_release_mapping);
-		mutex_unlock(&req->map->md->buf_mutex);
+		struct rio_mport_mapping *map = req->map;
+		struct mport_dev *md = map->md;
+
+		mutex_lock(&md->buf_mutex);
+		kref_put(&map->ref, mport_release_mapping);
+		mutex_unlock(&md->buf_mutex);
+
+		req->map = NULL;
 	}
 
 	kref_put(&priv->dma_ref, mport_release_dma);
_

Patches currently in -mm which might be from james010kim@gmail.com are

rapidio-mport_cdev-fix-use-after-free-in-dma_req_free.patch