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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. Fixes: 4b0986a36 ("rapidio: add mport character device support") Cc: stable@vger.kernel.org Signed-off-by: James Kim --- Changes since v1: - Rebased 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 | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c index 009b3b595bbf..9b94c9b2fad0 100644 --- a/drivers/rapidio/devices/rio_mport_cdev.c +++ b/drivers/rapidio/devices/rio_mport_cdev.c @@ -564,9 +564,14 @@ static void dma_req_free(struct kref *ref) } 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); -- 2.43.0