CVE-2024-36937 Affecting kernel-macros package, versions <5.14.21-150500.55.73.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-SLES155-KERNELMACROS-7703058
- published17 Aug 2024
- disclosed16 Aug 2024
Introduced: 16 Aug 2024
CVE-2024-36937 (opens in a new tab)How to fix?
Upgrade SLES:15.5 kernel-macros to version 5.14.21-150500.55.73.1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-macros package and not the kernel-macros package as distributed by SLES.
See How to fix? for SLES:15.5 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
xdp: use flags field to disambiguate broadcast redirect
When redirecting a packet using XDP, the bpf_redirect_map() helper will set up the redirect destination information in struct bpf_redirect_info (using the __bpf_xdp_redirect_map() helper function), and the xdp_do_redirect() function will read this information after the XDP program returns and pass the frame on to the right redirect destination.
When using the BPF_F_BROADCAST flag to do multicast redirect to a whole map, __bpf_xdp_redirect_map() sets the 'map' pointer in struct bpf_redirect_info to point to the destination map to be broadcast. And xdp_do_redirect() reacts to the value of this map pointer to decide whether it's dealing with a broadcast or a single-value redirect. However, if the destination map is being destroyed before xdp_do_redirect() is called, the map pointer will be cleared out (by bpf_clear_redirect_map()) without waiting for any XDP programs to stop running. This causes xdp_do_redirect() to think that the redirect was to a single target, but the target pointer is also NULL (since broadcast redirects don't have a single target), so this causes a crash when a NULL pointer is passed to dev_map_enqueue().
To fix this, change xdp_do_redirect() to react directly to the presence of the BPF_F_BROADCAST flag in the 'flags' value in struct bpf_redirect_info to disambiguate between a single-target and a broadcast redirect. And only read the 'map' pointer if the broadcast flag is set, aborting if that has been cleared out in the meantime. This prevents the crash, while keeping the atomic (cmpxchg-based) clearing of the map pointer itself, and without adding any more checks in the non-broadcast fast path.
References
- https://www.suse.com/security/cve/CVE-2024-36937.html
- https://bugzilla.suse.com/1225834
- https://git.kernel.org/stable/c/12481f30128fbebc2eeb55eb2d56390fdfa30c5e
- https://git.kernel.org/stable/c/272bfb019f3cc018f654b992115774e77b4f3ffc
- https://git.kernel.org/stable/c/5bcf0dcbf9066348058b88a510c57f70f384c92c
- https://git.kernel.org/stable/c/6fd81f9d333e7b3532036577b1beb74ba1323553
- https://git.kernel.org/stable/c/e22e25820fa04ea5eaac4ef7ee200e9923f466a4