{"id":"CVE-2024-36937","summary":"xdp: use flags field to disambiguate broadcast redirect","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxdp: use flags field to disambiguate broadcast redirect\n\nWhen redirecting a packet using XDP, the bpf_redirect_map() helper will set\nup the redirect destination information in struct bpf_redirect_info (using\nthe __bpf_xdp_redirect_map() helper function), and the xdp_do_redirect()\nfunction will read this information after the XDP program returns and pass\nthe frame on to the right redirect destination.\n\nWhen using the BPF_F_BROADCAST flag to do multicast redirect to a whole\nmap, __bpf_xdp_redirect_map() sets the 'map' pointer in struct\nbpf_redirect_info to point to the destination map to be broadcast. And\nxdp_do_redirect() reacts to the value of this map pointer to decide whether\nit's dealing with a broadcast or a single-value redirect. However, if the\ndestination map is being destroyed before xdp_do_redirect() is called, the\nmap pointer will be cleared out (by bpf_clear_redirect_map()) without\nwaiting for any XDP programs to stop running. This causes xdp_do_redirect()\nto think that the redirect was to a single target, but the target pointer\nis also NULL (since broadcast redirects don't have a single target), so\nthis causes a crash when a NULL pointer is passed to dev_map_enqueue().\n\nTo fix this, change xdp_do_redirect() to react directly to the presence of\nthe BPF_F_BROADCAST flag in the 'flags' value in struct bpf_redirect_info\nto disambiguate between a single-target and a broadcast redirect. And only\nread the 'map' pointer if the broadcast flag is set, aborting if that has\nbeen cleared out in the meantime. This prevents the crash, while keeping\nthe atomic (cmpxchg-based) clearing of the map pointer itself, and without\nadding any more checks in the non-broadcast fast path.","modified":"2026-04-16T04:40:01.246350225Z","published":"2024-05-30T15:29:26.353Z","related":["SUSE-SU-2024:2372-1","SUSE-SU-2024:2394-1","SUSE-SU-2024:2571-1","SUSE-SU-2024:2896-1","SUSE-SU-2024:2939-1","SUSE-SU-2024:2973-1","SUSE-SU-2025:20008-1","SUSE-SU-2025:20028-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/36xxx/CVE-2024-36937.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/12481f30128fbebc2eeb55eb2d56390fdfa30c5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/272bfb019f3cc018f654b992115774e77b4f3ffc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5bcf0dcbf9066348058b88a510c57f70f384c92c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6fd81f9d333e7b3532036577b1beb74ba1323553"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e22e25820fa04ea5eaac4ef7ee200e9923f466a4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/36xxx/CVE-2024-36937.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-36937"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"e624d4ed4aa8cc3c69d1359b0aaea539203ed266"},{"fixed":"12481f30128fbebc2eeb55eb2d56390fdfa30c5e"},{"fixed":"272bfb019f3cc018f654b992115774e77b4f3ffc"},{"fixed":"e22e25820fa04ea5eaac4ef7ee200e9923f466a4"},{"fixed":"6fd81f9d333e7b3532036577b1beb74ba1323553"},{"fixed":"5bcf0dcbf9066348058b88a510c57f70f384c92c"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-36937.json"}}],"schema_version":"1.7.5"}