# CVE-2021-47391: linux: In the Linux kernel, the following vulnerability has been resolved:  RDMA/cma: Ensure rdma_addr_cancel() happens befo...

CVE-2021-47391 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47391, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47391
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  RDMA/cma: Ensure rdma_addr_cancel() happens before issuing more requests  The FSM can run in a circle allowing rdma_resolve_ip() to be called twice on the same id_priv. While this cannot happen without going through the work, it violates the invariant that the same address resolution background request cannot be active twice.         CPU 1                                  CPU 2  rdma_resolve_addr():   RDMA_CM_IDLE -> RDMA_CM_ADDR_QUERY   rdma_resolve_ip(addr_handler)  #1  			 process_one_req(): for #1                           addr_handler():                             RDMA_CM_ADDR_QUERY -> RDMA_CM_ADDR_BOUND                             mutex_unlock(&id_priv->handler_mutex);                             [.. handler still running ..]  rdma_resolve_addr():   RDMA_CM_ADDR_BOUND -> RDMA_CM_ADDR_QUERY   rdma_resolve_ip(addr_handler)     !! two requests are now on the req_list  rdma_destroy_id():  destroy_id_handler_unlock():   _destroy_id():    cma_cancel_operation():     rdma_addr_cancel()                            // process_one_req() self removes it 		          spin_lock_bh(&lock);                            cancel_delayed_work(&req->work); 	                   if (!list_empty(&req->list)) == true        ! rdma_addr_cancel() returns after process_on_req #1 is done     kfree(id_priv)  			 process_one_req(): for #2                           addr_handler(): 	                    mutex_lock(&id_priv->handler_mutex);                             !! Use after free on id_priv  rdma_addr_cancel() expects there to be one req on the list and only cancels the first one. The self-removal behavior of the work only happens after the handler has returned. This yields a situations where the req_list can have two reqs for the same "handle" but rdma_addr_cancel() only cancels the first one.  The second req remains active beyond rdma_destroy_id() and will use-after-free id_priv once it inevitably triggers.  Fix this by remembering if the id_priv has called rdma_resolve_ip() and always cancel before calling it again. This ensures the req_list never gets more than one item in it and doesn't cost anything in the normal flow that never uses this strange error path.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.14.12-1 | [DEBIAN-CVE-2021-47391](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47391.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.14.12-1 | [DEBIAN-CVE-2021-47391](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47391.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.14.12-1 | [DEBIAN-CVE-2021-47391](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47391.md) | May 21, 2024 |

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