cve-2024-36937
Vulnerability from cvelistv5
Published
2024-05-30 15:29
Modified
2024-12-19 09:02
Severity ?
Summary
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
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/12481f30128fbebc2eeb55eb2d56390fdfa30c5e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/272bfb019f3cc018f654b992115774e77b4f3ffc
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5bcf0dcbf9066348058b88a510c57f70f384c92c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6fd81f9d333e7b3532036577b1beb74ba1323553
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e22e25820fa04ea5eaac4ef7ee200e9923f466a4
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/12481f30128fbebc2eeb55eb2d56390fdfa30c5e
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/272bfb019f3cc018f654b992115774e77b4f3ffc
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/5bcf0dcbf9066348058b88a510c57f70f384c92c
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/6fd81f9d333e7b3532036577b1beb74ba1323553
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/e22e25820fa04ea5eaac4ef7ee200e9923f466a4
Impacted products
Vendor Product Version
Linux Linux Version: 5.14
Show details on NVD website

To clipboard 

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And\\nxdp_do_redirect() reacts to the value of this map pointer to decide whether\\nit\u0027s 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\u0027t 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 \u0027flags\u0027 value in struct bpf_redirect_info\\nto disambiguate between a single-target and a broadcast redirect. And only\\nread the \u0027map\u0027 pointer if the broadcast flag is set, aborting if that has\\nbeen cleared out in the meantime. 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Cuando se utiliza el indicador BPF_F_BROADCAST para realizar una redirecci\u00f3n de multidifusi\u00f3n a un mapa completo, __bpf_xdp_redirect_map() establece el puntero \u0027mapa\u0027 en la estructura bpf_redirect_info para que apunte al mapa de destino que se va a transmitir. Y xdp_do_redirect() reacciona al valor de este puntero de mapa para decidir si se trata de una transmisi\u00f3n o una redirecci\u00f3n de valor \u00fanico. Sin embargo, si el mapa de destino se destruye antes de llamar a xdp_do_redirect(), el puntero del mapa se borrar\u00e1 (mediante bpf_clear_redirect_map()) sin esperar a que deje de ejecutarse ning\u00fan programa XDP. Esto hace que xdp_do_redirect() piense que la redirecci\u00f3n fue a un \u00fanico objetivo, pero el puntero de destino tambi\u00e9n es NULL (dado que las redirecciones de difusi\u00f3n no tienen un \u00fanico objetivo), por lo que esto provoca un bloqueo cuando se pasa un puntero NULL a dev_map_enqueue( ). 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}


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