{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-21881", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.782Z", "datePublished": "2025-03-27T14:57:10.241Z", "dateUpdated": "2026-05-11T21:08:19.723Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T21:08:19.723Z"}, "descriptions": [{"lang": "en", "value": "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 <TASK>\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": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/uprobes.c"], "versions": [{"version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "lessThan": "c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e", "status": "affected", "versionType": "git"}, {"version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "lessThan": "0b6f19714588cf2366b0364234f97ba963688f63", "status": "affected", "versionType": "git"}, {"version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "lessThan": "13cca2b73e2b0ec3ea6d6615d615395621d22752", "status": "affected", "versionType": "git"}, {"version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "lessThan": "54011fc94422f094eaf47555284de70a4bc32bb9", "status": "affected", "versionType": "git"}, {"version": "2b144498350860b6ee9dc57ff27a93ad488de5dc", "lessThan": "bddf10d26e6e5114e7415a0e442ec6f51a559468", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/events/uprobes.c"], "versions": [{"version": "3.5", "status": "affected"}, {"version": "0", "lessThan": "3.5", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.130", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.81", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.18", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.13.6", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.14", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5", "versionEndExcluding": "6.1.130"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5", "versionEndExcluding": "6.6.81"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5", "versionEndExcluding": "6.12.18"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5", "versionEndExcluding": "6.13.6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.5", "versionEndExcluding": "6.14"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e"}, {"url": "https://git.kernel.org/stable/c/0b6f19714588cf2366b0364234f97ba963688f63"}, {"url": "https://git.kernel.org/stable/c/13cca2b73e2b0ec3ea6d6615d615395621d22752"}, {"url": "https://git.kernel.org/stable/c/54011fc94422f094eaf47555284de70a4bc32bb9"}, {"url": "https://git.kernel.org/stable/c/bddf10d26e6e5114e7415a0e442ec6f51a559468"}], "title": "uprobes: Reject the shared zeropage in uprobe_write_opcode()", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T19:38:38.879Z"}}]}}

{}

{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3493C8F1-7D86-400D-B13B-BE0A4FADAE02", "versionEndExcluding": "6.1.130", "versionStartIncluding": "3.5", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "8C92C9CD-2ADE-412E-A7FF-DC9E0630B25D", "versionEndExcluding": "6.6.81", "versionStartIncluding": "6.2", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3D5C8D9A-4013-4C1A-810F-AA540BB5737C", "versionEndExcluding": "6.12.18", "versionStartIncluding": "6.7", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "64F12D9B-71C2-4CD7-A288-0D5EF1709620", "versionEndExcluding": "6.13.6", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*", "matchCriteriaId": "186716B6-2B66-4BD0-852E-D48E71C0C85F", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D3E781C-403A-498F-9DA9-ECEE50F41E75", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc3:*:*:*:*:*:*", "matchCriteriaId": "66619FB8-0AAF-4166-B2CF-67B24143261D", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc4:*:*:*:*:*:*", "matchCriteriaId": "D3D6550E-6679-4560-902D-AF52DCFE905B", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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 <TASK>\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 ]"}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: uprobes: Rechazar la p\u00e1gina cero compartida en uprobe_write_opcode() Activamos el siguiente fallo en las pruebas de syzkaller: ERROR: Estado de p\u00e1gina incorrecto en el proceso syz.7.38 pfn:1eff3 page: refcount:0 mapcount:0 mapping:000000000000000 index:0x0 pfn:0x1eff3 flags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff) raw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 000000000000000 raw: 000000000000000 0000000000000000 00000000ffffffffe 0000000000000000 p\u00e1gina volcada porque: PAGE_FLAGS_CHECK_AT_FREE indicador(es) establecido(s) Nombre del hardware: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 01/04/2014 Seguimiento de llamadas: dump_stack_lvl+0x32/0x50 bad_page+0x69/0xf0 free_unref_page_prepare+0x401/0x500 free_unref_page+0x6d/0x1b0 uprobe_write_opcode+0x460/0x8e0 install_breakpoint.part.0+0x51/0x80 register_for_each_vma+0x1d9/0x2b0 __uprobe_register+0x245/0x300 bpf_uprobe_multi_link_attach+0x29b/0x4f0 link_create+0x1e2/0x280 __sys_bpf+0x75f/0xac0 __x64_sys_bpf+0x1a/0x30 do_syscall_64+0x56/0x100 entry_SYSCALL_64_after_hwframe+0x78/0xe2 BUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1 The following syzkaller test case can be used to reproduce: r2 = creat(&amp;(0x7f0000000000)='./file0\\x00', 0x8) write$nbd(r2, &amp;(0x7f0000000580)=ANY=[], 0x10) r4 = openat(0xffffffffffffff9c, &amp;(0x7f0000000040)='./file0\\x00', 0x42, 0x0) mmap$IORING_OFF_SQ_RING(&amp;(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0) r5 = userfaultfd(0x80801) ioctl$UFFDIO_API(r5, 0xc018aa3f, &amp;(0x7f0000000040)={0xaa, 0x20}) r6 = userfaultfd(0x80801) ioctl$UFFDIO_API(r6, 0xc018aa3f, &amp;(0x7f0000000140)) ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &amp;(0x7f0000000100)={{&amp;(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2}) ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &amp;(0x7f0000000000)={{&amp;(0x7f0000ffd000/0x1000)=nil, 0x1000}}) r7 = bpf$PROG_LOAD(0x5, &amp;(0x7f0000000140)={0x2, 0x3, &amp;(0x7f0000000200)=ANY=[@ANYBLOB=\"1800000000120000000000000000000095\"], &amp;(0x7f0000000000)='GPL\\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94) bpf$BPF_LINK_CREATE_XDP(0x1c, &amp;(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&amp;(0x7f0000000080)='./file0\\x00', &amp;(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40) La causa es que cero El pfn se establece en el PTE sin aumentar el recuento RSS en mfill_atomic_pte_zeropage() y el recuento de referencias del folio cero no aumenta en consecuencia. Luego, se realiza la misma operaci\u00f3n en el pfn en uprobe_write_opcode()-&gt;__replace_page() para disminuir incondicionalmente el recuento RSS y el recuento de referencias de old_folio. Por lo tanto, se introducen dos errores: 1. El recuento RSS es incorrecto; al finalizar el proceso, check_mm() informa el error \"Bad RSS-count\" (recuento RSS incorrecto). 2. El folio reservado (folio cero) se libera cuando folio-&gt;refcount es cero; entonces, free_pages_prepare-&gt;free_page_is_bad() informa el error \"Bad page state\" (estado de p\u00e1gina incorrecto). Hay m\u00e1s, la siguiente advertencia tambi\u00e9n podr\u00eda activarse te\u00f3ricamente: __replace_page() -&gt; ... -&gt; folio_remove_rmap_pte() -&gt; VM_WARN_ON_FOLIO(is_zero_folio(folio), folio) Teniendo en cuenta que el impacto de uprobe en el folio cero es un caso muy raro, simplemente rechace el folio antiguo cero inmediatamente despu\u00e9s de get_user_page_vma_remote(). [ mingo: Se limpi\u00f3 el registro de cambios ]"}], "id": "CVE-2025-21881", "lastModified": "2025-11-03T20:17:25.100", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-03-27T15:15:56.000", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0b6f19714588cf2366b0364234f97ba963688f63"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/13cca2b73e2b0ec3ea6d6615d615395621d22752"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/54011fc94422f094eaf47555284de70a4bc32bb9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/bddf10d26e6e5114e7415a0e442ec6f51a559468"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: uprobes: Reject the shared zeropage in uprobe_write_opcode()", "id": "2355422", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2355422"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nuprobes: Reject the shared zeropage in uprobe_write_opcode()\nWe triggered the following crash in syzkaller tests:\nBUG: Bad page state in process syz.7.38 pfn:1eff3\npage: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1eff3\nflags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff)\nraw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 0000000000000000\nraw: 0000000000000000 0000000000000000 00000000fffffffe 0000000000000000\npage dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014\nCall Trace:\n<TASK>\ndump_stack_lvl+0x32/0x50\nbad_page+0x69/0xf0\nfree_unref_page_prepare+0x401/0x500\nfree_unref_page+0x6d/0x1b0\nuprobe_write_opcode+0x460/0x8e0\ninstall_breakpoint.part.0+0x51/0x80\nregister_for_each_vma+0x1d9/0x2b0\n__uprobe_register+0x245/0x300\nbpf_uprobe_multi_link_attach+0x29b/0x4f0\nlink_create+0x1e2/0x280\n__sys_bpf+0x75f/0xac0\n__x64_sys_bpf+0x1a/0x30\ndo_syscall_64+0x56/0x100\nentry_SYSCALL_64_after_hwframe+0x78/0xe2\nBUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1\nThe following syzkaller test case can be used to reproduce:\nr2 = creat(&(0x7f0000000000)='./file0\\x00', 0x8)\nwrite$nbd(r2, &(0x7f0000000580)=ANY=[], 0x10)\nr4 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\\x00', 0x42, 0x0)\nmmap$IORING_OFF_SQ_RING(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0)\nr5 = userfaultfd(0x80801)\nioctl$UFFDIO_API(r5, 0xc018aa3f, &(0x7f0000000040)={0xaa, 0x20})\nr6 = userfaultfd(0x80801)\nioctl$UFFDIO_API(r6, 0xc018aa3f, &(0x7f0000000140))\nioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &(0x7f0000000100)={{&(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2})\nioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &(0x7f0000000000)={{&(0x7f0000ffd000/0x1000)=nil, 0x1000}})\nr7 = bpf$PROG_LOAD(0x5, &(0x7f0000000140)={0x2, 0x3, &(0x7f0000000200)=ANY=[@ANYBLOB=\"1800000000120000000000000000000095\"], &(0x7f0000000000)='GPL\\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94)\nbpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&(0x7f0000000080)='./file0\\x00', &(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40)\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.\nTherefore, two bugs are introduced:\n1. The RSS count is incorrect, when process exit, the check_mm() report\nerror \"Bad rss-count\".\n2. The reserved folio (zero folio) is freed when folio->refcount is zero,\nthen free_pages_prepare->free_page_is_bad() report error\n\"Bad page state\".\nThere is more, the following warning could also theoretically be triggered:\n__replace_page()\n-> ...\n-> folio_remove_rmap_pte()\n-> VM_WARN_ON_FOLIO(is_zero_folio(folio), folio)\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[ mingo: Cleaned up the changelog ]"], "name": "CVE-2025-21881", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-03-27T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-21881\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21881\nhttps://lore.kernel.org/linux-cve-announce/2025032712-CVE-2025-21881-7a0f@gregkh/T"], "threat_severity": "Low"}

{}