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rapidio: mport_cdev: fix use-after-free in dma_req_free()

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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.

Link: https://lore.kernel.org/20260723235220.588424-1-james010kim@gmail.com
Fixes: e8de370188 ("rapidio: add mport char device driver")
Signed-off-by: James Kim <james010kim@gmail.com>
Reviewed-by: Dan Carpenter <error27@gmail.com>
Cc: Alexandre Bounine <alex.bou9@gmail.com>
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>
This commit is contained in:
James Kim
2026-07-24 08:52:20 +09:00
committed by Andrew Morton
parent 011291b70b
commit 5cbef379a9
1 changed files with 7 additions and 3 deletions
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10
drivers/rapidio/devices/rio_mport_cdev.c
View File

@@ -564,9 +564,13 @@ 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);
req->map = NULL;
kref_put(&map->ref, mport_release_mapping);
mutex_unlock(&md->buf_mutex);
}
kref_put(&priv->dma_ref, mport_release_dma);