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Thu, 23 Jul 2026 16:53:20 -0700 (PDT) Received: from localhost.localdomain ([119.204.109.83]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cf8efde5cfsm41417575ad.31.2026.07.23.16.53.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2026 16:53:19 -0700 (PDT) From: James Kim To: linux-kernel@vger.kernel.org Cc: mporter@kernel.crashing.org, alex.bou9@gmail.com, akpm@linux-foundation.org, error27@gmail.com, gregkh@linuxfoundation.org, stable@vger.kernel.org, James Kim Subject: [PATCH v3] rapidio: mport_cdev: fix use-after-free in dma_req_free() Date: Fri, 24 Jul 2026 08:52:20 +0900 Message-Id: <20260723235220.588424-1-james010kim@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260615070530.371640-1-james010kim@gmail.com> References: <20260615070530.371640-1-james010kim@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" dma_req_free() acquires buf_mutex through req->map, drops the mapping reference with kref_put(), 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(), clearing req->map while holding buf_mutex, and using the cached md for mutex unlocking. The bug is reachable from userspace via the RapidIO mport character device interface. Fixes: e8de370188d0 ("rapidio: add mport char device driver") Cc: stable@vger.kernel.org Reviewed-by: Dan Carpenter Signed-off-by: James Kim --- Changes since v2: - Correct the Fixes tag. - Clear req->map while holding buf_mutex. - Clarify that the bug is reachable from userspace. - Update Dan Carpenter's email address and add his Reviewed-by tag. Changes since v1: - Rebase on v7.1. - Add Dan Carpenter to Cc for lifetime and use-after-free review. - No functional changes. --- drivers/rapidio/devices/rio_mport_cdev.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/dev= ices/rio_mport_cdev.c index 009b3b595bbf..ad82c2108a56 100644 --- a/drivers/rapidio/devices/rio_mport_cdev.c +++ b/drivers/rapidio/devices/rio_mport_cdev.c @@ -564,9 +564,13 @@ static void dma_req_free(struct kref *ref) } =20 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 =3D req->map; + struct mport_dev *md =3D map->md; + + mutex_lock(&md->buf_mutex); + req->map =3D NULL; + kref_put(&map->ref, mport_release_mapping); + mutex_unlock(&md->buf_mutex); } =20 kref_put(&priv->dma_ref, mport_release_dma); --=20 2.25.1