{"cve":"CVE-2025-21866","nvd":{"published":"2025-03-12T10:15:19.800","modified":"2026-06-17T08:44:29.233","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/code-patching: Fix KASAN hit by not flagging text patching area as VM_ALLOC\n\nErhard reported the following KASAN hit while booting his PowerMac G4\nwith a KASAN-enabled kernel 6.13-rc6:\n\n  BUG: KASAN: vmalloc-out-of-bounds in copy_to_kernel_nofault+0xd8/0x1c8\n  Write of size 8 at addr f1000000 by task chronyd/1293\n\n  CPU: 0 UID: 123 PID: 1293 Comm: chronyd Tainted: G        W          6.13.0-rc6-PMacG4 #2\n  Tainted: [W]=WARN\n  Hardware name: PowerMac3,6 7455 0x80010303 PowerMac\n  Call Trace:\n  [c2437590] [c1631a84] dump_stack_lvl+0x70/0x8c (unreliable)\n  [c24375b0] [c0504998] print_report+0xdc/0x504\n  [c2437610] [c050475c] kasan_report+0xf8/0x108\n  [c2437690] [c0505a3c] kasan_check_range+0x24/0x18c\n  [c24376a0] [c03fb5e4] copy_to_kernel_nofault+0xd8/0x1c8\n  [c24376c0] [c004c014] patch_instructions+0x15c/0x16c\n  [c2437710] [c00731a8] bpf_arch_text_copy+0x60/0x7c\n  [c2437730] [c0281168] bpf_jit_binary_pack_finalize+0x50/0xac\n  [c2437750] [c0073cf4] bpf_int_jit_compile+0xb30/0xdec\n  [c2437880] [c0280394] bpf_prog_select_runtime+0x15c/0x478\n  [c24378d0] [c1263428] bpf_prepare_filter+0xbf8/0xc14\n  [c2437990] [c12677ec] bpf_prog_create_from_user+0x258/0x2b4\n  [c24379d0] [c027111c] do_seccomp+0x3dc/0x1890\n  [c2437ac0] [c001d8e0] system_call_exception+0x2dc/0x420\n  [c2437f30] [c00281ac] ret_from_syscall+0x0/0x2c\n  --- interrupt: c00 at 0x5a1274\n  NIP:  005a1274 LR: 006a3b3c CTR: 005296c8\n  REGS: c2437f40 TRAP: 0c00   Tainted: G        W           (6.13.0-rc6-PMacG4)\n  MSR:  0200f932 <VEC,EE,PR,FP,ME,IR,DR,RI>  CR: 24004422  XER: 00000000\n\n  GPR00: 00000166 af8f3fa0 a7ee3540 00000001 00000000 013b6500 005a5858 0200f932\n  GPR08: 00000000 00001fe9 013d5fc8 005296c8 2822244c 00b2fcd8 00000000 af8f4b57\n  GPR16: 00000000 00000001 00000000 00000000 00000000 00000001 00000000 00000002\n  GPR24: 00afdbb0 00000000 00000000 00000000 006e0004 013ce060 006e7c1c 00000001\n  NIP [005a1274] 0x5a1274\n  LR [006a3b3c] 0x6a3b3c\n  --- interrupt: c00\n\n  The buggy address belongs to the virtual mapping at\n   [f1000000, f1002000) created by:\n   text_area_cpu_up+0x20/0x190\n\n  The buggy address belongs to the physical page:\n  page: refcount:1 mapcount:0 mapping:00000000 index:0x0 pfn:0x76e30\n  flags: 0x80000000(zone=2)\n  raw: 80000000 00000000 00000122 00000000 00000000 00000000 ffffffff 00000001\n  raw: 00000000\n  page dumped because: kasan: bad access detected\n\n  Memory state around the buggy address:\n   f0ffff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n   f0ffff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n  >f1000000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n             ^\n   f1000080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n   f1000100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8\n  ==================================================================\n\nf8 corresponds to KASAN_VMALLOC_INVALID which means the area is not\ninitialised hence not supposed to be used yet.\n\nPowerpc text patching infrastructure allocates a virtual memory area\nusing get_vm_area() and flags it as VM_ALLOC. But that flag is meant\nto be used for vmalloc() and vmalloc() allocated memory is not\nsupposed to be used before a call to __vmalloc_node_range() which is\nnever called for that area.\n\nThat went undetected until commit e4137f08816b (\"mm, kasan, kmsan:\ninstrument copy_from/to_kernel_nofault\")\n\nThe area allocated by text_area_cpu_up() is not vmalloc memory, it is\nmapped directly on demand when needed by map_kernel_page(). There is\nno VM flag corresponding to such usage, so just pass no flag. That way\nthe area will be unpoisonned and usable immediately.","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":["CWE-770"],"references":["https://git.kernel.org/stable/c/2d542f13d26344e3452eee77613026ce9b653065","https://git.kernel.org/stable/c/2e6c80423f201405fd65254e52decd21663896f3","https://git.kernel.org/stable/c/6847b3e40bb963e57b61d1cc6fe84cb37b9d3d4c","https://git.kernel.org/stable/c/8d06e9208184b2851fa79a3a39d6860320c8bdf8","https://git.kernel.org/stable/c/97de5852058a299ba447cd9782fe96488d30108b"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:00:17.429720821+00:00"},"epss":{"cve":"CVE-2025-21866","score":0.0025,"percentile":0.16453,"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."]}