{"cve":"CVE-2024-39488","nvd":{"published":"2024-07-10T08:15:11.003","modified":"2026-06-17T07:42:01.567","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\narm64: asm-bug: Add .align 2 to the end of __BUG_ENTRY\n\nWhen CONFIG_DEBUG_BUGVERBOSE=n, we fail to add necessary padding bytes\nto bug_table entries, and as a result the last entry in a bug table will\nbe ignored, potentially leading to an unexpected panic(). All prior\nentries in the table will be handled correctly.\n\nThe arm64 ABI requires that struct fields of up to 8 bytes are\nnaturally-aligned, with padding added within a struct such that struct\nare suitably aligned within arrays.\n\nWhen CONFIG_DEBUG_BUGVERPOSE=y, the layout of a bug_entry is:\n\n\tstruct bug_entry {\n\t\tsigned int      bug_addr_disp;\t// 4 bytes\n\t\tsigned int      file_disp;\t// 4 bytes\n\t\tunsigned short  line;\t\t// 2 bytes\n\t\tunsigned short  flags;\t\t// 2 bytes\n\t}\n\n... with 12 bytes total, requiring 4-byte alignment.\n\nWhen CONFIG_DEBUG_BUGVERBOSE=n, the layout of a bug_entry is:\n\n\tstruct bug_entry {\n\t\tsigned int      bug_addr_disp;\t// 4 bytes\n\t\tunsigned short  flags;\t\t// 2 bytes\n\t\t< implicit padding >\t\t// 2 bytes\n\t}\n\n... with 8 bytes total, with 6 bytes of data and 2 bytes of trailing\npadding, requiring 4-byte alginment.\n\nWhen we create a bug_entry in assembly, we align the start of the entry\nto 4 bytes, which implicitly handles padding for any prior entries.\nHowever, we do not align the end of the entry, and so when\nCONFIG_DEBUG_BUGVERBOSE=n, the final entry lacks the trailing padding\nbytes.\n\nFor the main kernel image this is not a problem as find_bug() doesn't\ndepend on the trailing padding bytes when searching for entries:\n\n\tfor (bug = __start___bug_table; bug < __stop___bug_table; ++bug)\n\t\tif (bugaddr == bug_addr(bug))\n\t\t\treturn bug;\n\nHowever for modules, module_bug_finalize() depends on the trailing\nbytes when calculating the number of entries:\n\n\tmod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);\n\n... and as the last bug_entry lacks the necessary padding bytes, this entry\nwill not be counted, e.g. in the case of a single entry:\n\n\tsechdrs[i].sh_size == 6\n\tsizeof(struct bug_entry) == 8;\n\n\tsechdrs[i].sh_size / sizeof(struct bug_entry) == 0;\n\nConsequently module_find_bug() will miss the last bug_entry when it does:\n\n\tfor (i = 0; i < mod->num_bugs; ++i, ++bug)\n\t\tif (bugaddr == bug_addr(bug))\n\t\t\tgoto out;\n\n... which can lead to a kenrel panic due to an unhandled bug.\n\nThis can be demonstrated with the following module:\n\n\tstatic int __init buginit(void)\n\t{\n\t\tWARN(1, \"hello\\n\");\n\t\treturn 0;\n\t}\n\n\tstatic void __exit bugexit(void)\n\t{\n\t}\n\n\tmodule_init(buginit);\n\tmodule_exit(bugexit);\n\tMODULE_LICENSE(\"GPL\");\n\n... which will trigger a kernel panic when loaded:\n\n\t------------[ cut here ]------------\n\thello\n\tUnexpected kernel BRK exception at EL1\n\tInternal error: BRK handler: 00000000f2000800 [#1] PREEMPT SMP\n\tModules linked in: hello(O+)\n\tCPU: 0 PID: 50 Comm: insmod Tainted: G           O       6.9.1 #8\n\tHardware name: linux,dummy-virt (DT)\n\tpstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)\n\tpc : buginit+0x18/0x1000 [hello]\n\tlr : buginit+0x18/0x1000 [hello]\n\tsp : ffff800080533ae0\n\tx29: ffff800080533ae0 x28: 0000000000000000 x27: 0000000000000000\n\tx26: ffffaba8c4e70510 x25: ffff800080533c30 x24: ffffaba8c4a28a58\n\tx23: 0000000000000000 x22: 0000000000000000 x21: ffff3947c0eab3c0\n\tx20: ffffaba8c4e3f000 x19: ffffaba846464000 x18: 0000000000000006\n\tx17: 0000000000000000 x16: ffffaba8c2492834 x15: 0720072007200720\n\tx14: 0720072007200720 x13: ffffaba8c49b27c8 x12: 0000000000000312\n\tx11: 0000000000000106 x10: ffffaba8c4a0a7c8 x9 : ffffaba8c49b27c8\n\tx8 : 00000000ffffefff x7 : ffffaba8c4a0a7c8 x6 : 80000000fffff000\n\tx5 : 0000000000000107 x4 : 0000000000000000 x3 : 0000000000000000\n\tx2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff3947c0eab3c0\n\tCall trace:\n\t buginit+0x18/0x1000 [hello]\n\t do_one_initcall+0x80/0x1c8\n\t do_init_module+0x60/0x218\n\t load_module+0x1ba4/0x1d70\n\t __do_sys_init_module+0x198/0x1d0\n\t __arm64_sys_init_module+0x1c/0x28\n\t invoke_syscall+0x48/0x114\n\t el0_svc\n---truncated---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/22469a0335a1a1a690349b58bcb55822457df81e","https://git.kernel.org/stable/c/3fd487ffaa697ddb05af78a75aaaddabe71c52b0","https://git.kernel.org/stable/c/461a760d578b2b2c2faac3040b6b7c77baf128f8","https://git.kernel.org/stable/c/9f2ad88f9b349554f64e4037ec185c84d7dd9c7d","https://git.kernel.org/stable/c/c1929c041a262a4a27265db8dce3619c92aa678c"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:52:42.518321223+00:00"},"epss":{"cve":"CVE-2024-39488","score":0.00237,"percentile":0.14733,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}