{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2025-21881", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2025-21881", "idYear": 2025, "status": "PUBLISHED", "publishedAt": "2025-03-27T14:57:10.241Z", "updatedAt": "2026-05-11T21:08:19.723Z", "importedAt": "2026-10-24T01:57:29.455Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "uprobes: Reject the shared zeropage in uprobe_write_opcode()", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nuprobes: Reject the shared zeropage in uprobe_write_opcode()\n\nWe triggered the following crash in syzkaller tests:\n\n BUG: Bad page state in process syz.7.38 pfn:1eff3\n page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1eff3\n flags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff)\n raw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 0000000000000000\n raw: 0000000000000000 0000000000000000 00000000fffffffe 0000000000000000\n page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014\n Call Trace:\n \n dump_stack_lvl+0x32/0x50\n bad_page+0x69/0xf0\n free_unref_page_prepare+0x401/0x500\n free_unref_page+0x6d/0x1b0\n uprobe_write_opcode+0x460/0x8e0\n install_breakpoint.part.0+0x51/0x80\n register_for_each_vma+0x1d9/0x2b0\n __uprobe_register+0x245/0x300\n bpf_uprobe_multi_link_attach+0x29b/0x4f0\n link_create+0x1e2/0x280\n __sys_bpf+0x75f/0xac0\n __x64_sys_bpf+0x1a/0x30\n do_syscall_64+0x56/0x100\n entry_SYSCALL_64_after_hwframe+0x78/0xe2\n\n BUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1\n\nThe following syzkaller test case can be used to reproduce:\n\n r2 = creat(&(0x7f0000000000)='./file0\\x00', 0x8)\n write$nbd(r2, &(0x7f0000000580)=ANY=[], 0x10)\n r4 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\\x00', 0x42, 0x0)\n mmap$IORING_OFF_SQ_RING(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0)\n r5 = userfaultfd(0x80801)\n ioctl$UFFDIO_API(r5, 0xc018aa3f, &(0x7f0000000040)={0xaa, 0x20})\n r6 = userfaultfd(0x80801)\n ioctl$UFFDIO_API(r6, 0xc018aa3f, &(0x7f0000000140))\n ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &(0x7f0000000100)={{&(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2})\n ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &(0x7f0000000000)={{&(0x7f0000ffd000/0x1000)=nil, 0x1000}})\n r7 = bpf$PROG_LOAD(0x5, &(0x7f0000000140)={0x2, 0x3, &(0x7f0000000200)=ANY=[@ANYBLOB=\"1800000000120000000000000000000095\"], &(0x7f0000000000)='GPL\\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94)\n bpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&(0x7f0000000080)='./file0\\x00', &(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40)\n\nThe cause is that zero pfn is set to the PTE without increasing the RSS\ncount in mfill_atomic_pte_zeropage() and the refcount of zero folio does\nnot increase accordingly. Then, the operation on the same pfn is performed\nin uprobe_write_opcode()->__replace_page() to unconditional decrease the\nRSS count and old_folio's refcount.\n\nTherefore, two bugs are introduced:\n\n 1. The RSS count is incorrect, when process exit, the check_mm() report\n error \"Bad rss-count\".\n\n 2. The reserved folio (zero folio) is freed when folio->refcount is zero,\n then free_pages_prepare->free_page_is_bad() report error\n \"Bad page state\".\n\nThere is more, the following warning could also theoretically be triggered:\n\n __replace_page()\n -> ...\n -> folio_remove_rmap_pte()\n -> VM_WARN_ON_FOLIO(is_zero_folio(folio), folio)\n\nConsidering that uprobe hit on the zero folio is a very rare case, just\nreject zero old folio immediately after get_user_page_vma_remote().\n\n[ mingo: Cleaned up the changelog ]", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "status": "affected", "versionType": "git", "lessThan": "c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e" }, { "version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "status": "affected", "versionType": "git", "lessThan": "0b6f19714588cf2366b0364234f97ba963688f63" }, { "version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "status": "affected", "versionType": "git", "lessThan": "13cca2b73e2b0ec3ea6d6615d615395621d22752" }, { "version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "status": "affected", "versionType": "git", "lessThan": "54011fc94422f094eaf47555284de70a4bc32bb9" }, { "version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "status": "affected", "versionType": "git", "lessThan": "bddf10d26e6e5114e7415a0e442ec6f51a559468" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "3.5", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "3.5" }, { "version": "6.1.130", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.81", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.18", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.13.6", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.13.*" }, { "version": "6.14", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }