{"id":"CVE-2024-47702","summary":"bpf: Fail verification for sign-extension of packet data/data_end/data_meta","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fail verification for sign-extension of packet data/data_end/data_meta\n\nsyzbot reported a kernel crash due to\n  commit 1f1e864b6555 (\"bpf: Handle sign-extenstin ctx member accesses\").\nThe reason is due to sign-extension of 32-bit load for\npacket data/data_end/data_meta uapi field.\n\nThe original code looks like:\n        r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u003edata */\n        r3 = *(u32 *)(r1 + 80) /* load __sk_buff-\u003edata_end */\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto +1\n        ...\nNote that __sk_buff-\u003edata load has 32-bit sign extension.\n\nAfter verification and convert_ctx_accesses(), the final asm code looks like:\n        r2 = *(u64 *)(r1 +208)\n        r2 = (s32)r2\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\n        ...\nNote that 'r2 = (s32)r2' may make the kernel __sk_buff-\u003edata address invalid\nwhich may cause runtime failure.\n\nCurrently, in C code, typically we have\n        void *data = (void *)(long)skb-\u003edata;\n        void *data_end = (void *)(long)skb-\u003edata_end;\n        ...\nand it will generate\n        r2 = *(u64 *)(r1 +208)\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\n\nIf we allow sign-extension,\n        void *data = (void *)(long)(int)skb-\u003edata;\n        void *data_end = (void *)(long)skb-\u003edata_end;\n        ...\nthe generated code looks like\n        r2 = *(u64 *)(r1 +208)\n        r2 \u003c\u003c= 32\n        r2 s\u003e\u003e= 32\n        r3 = *(u64 *)(r1 +80)\n        r0 = r2\n        r0 += 8\n        if r3 \u003e r0 goto pc+1\nand this will cause verification failure since \"r2 \u003c\u003c= 32\" is not allowed\nas \"r2\" is a packet pointer.\n\nTo fix this issue for case\n  r2 = *(s32 *)(r1 + 76) /* load __sk_buff-\u003edata */\nthis patch added additional checking in is_valid_access() callback\nfunction for packet data/data_end/data_meta access. If those accesses\nare with sign-extenstion, the verification will fail.\n\n  [1] https://lore.kernel.org/bpf/000000000000c90eee061d236d37@google.com/","modified":"2026-03-20T12:38:04.925524Z","published":"2024-10-21T11:53:37.958Z","related":["SUSE-SU-2024:3984-1","SUSE-SU-2024:3986-1","SUSE-SU-2024:4318-1","SUSE-SU-2024:4387-1","SUSE-SU-2025:20163-1","SUSE-SU-2025:20164-1","SUSE-SU-2025:20246-1","SUSE-SU-2025:20247-1","USN-7276-1","USN-7277-1","openSUSE-SU-2024:14500-1","openSUSE-SU-2025:14705-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/47xxx/CVE-2024-47702.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/92de36080c93296ef9005690705cba260b9bd68a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f09757fe97a225ae505886eac572e4cbfba96537"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f1620c93a1ec950d87ef327a565d3907736d3340"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/47xxx/CVE-2024-47702.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-47702"},{"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":"1f1e864b65554e33fe74e3377e58b12f4302f2eb"},{"fixed":"f1620c93a1ec950d87ef327a565d3907736d3340"},{"fixed":"f09757fe97a225ae505886eac572e4cbfba96537"},{"fixed":"92de36080c93296ef9005690705cba260b9bd68a"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2024-47702.json"}}],"schema_version":"1.7.5"}