# CVE-2021-47261: linux: In the Linux kernel, the following vulnerability has been resolved:  IB/mlx5: Fix initializing CQ fragments buffer  T...

CVE-2021-47261 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47261, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47261
- 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:  IB/mlx5: Fix initializing CQ fragments buffer  The function init_cq_frag_buf() can be called to initialize the current CQ fragments buffer cq->buf, or the temporary cq->resize_buf that is filled during CQ resize operation.  However, the offending commit started to use function get_cqe() for getting the CQEs, the issue with this change is that get_cqe() always returns CQEs from cq->buf, which leads us to initialize the wrong buffer, and in case of enlarging the CQ we try to access elements beyond the size of the current cq->buf and eventually hit a kernel panic.   [exception RIP: init_cq_frag_buf+103]   [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib]   [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core]   [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt]   [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt]   [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt]   [ffff9f799ddcbec8] kthread at ffffffffa66c5da1   [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd  Fix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that takes the correct source buffer as a parameter.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.10.46-1 | [DEBIAN-CVE-2021-47261](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47261.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.10.46-1 | [DEBIAN-CVE-2021-47261](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47261.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.10.46-1 | [DEBIAN-CVE-2021-47261](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47261.md) | May 21, 2024 |

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