{"dataType": "CVE_RECORD", "dataVersion": "5.1", "cveMetadata": {"cveId": "CVE-2025-40040", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.154Z", "datePublished": "2025-10-28T11:48:20.395Z", "dateUpdated": "2025-10-29T13:19:40.112Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-10-29T13:19:40.112Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/ksm: fix flag-dropping behavior in ksm_madvise\n\nsyzkaller discovered the following crash: (kernel BUG)\n\n[ 44.607039] ------------[ cut here ]------------\n[ 44.607422] kernel BUG at mm/userfaultfd.c:2067!\n[ 44.608148] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted 6.16.0-rc6 #1 PREEMPT(none)\n[ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[ 44.610695] RIP: 0010:userfaultfd_release_all+0x3a8/0x460\n\n<snip other registers, drop unreliable trace>\n\n[ 44.617726] Call Trace:\n[ 44.617926] <TASK>\n[ 44.619284] userfaultfd_release+0xef/0x1b0\n[ 44.620976] __fput+0x3f9/0xb60\n[ 44.621240] fput_close_sync+0x110/0x210\n[ 44.622222] __x64_sys_close+0x8f/0x120\n[ 44.622530] do_syscall_64+0x5b/0x2f0\n[ 44.622840] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[ 44.623244] RIP: 0033:0x7f365bb3f227\n\nKernel panics because it detects UFFD inconsistency during\nuserfaultfd_release_all(). Specifically, a VMA which has a valid pointer\nto vma->vm_userfaultfd_ctx, but no UFFD flags in vma->vm_flags.\n\nThe inconsistency is caused in ksm_madvise(): when user calls madvise()\nwith MADV_UNMEARGEABLE on a VMA that is registered for UFFD in MINOR mode,\nit accidentally clears all flags stored in the upper 32 bits of\nvma->vm_flags.\n\nAssuming x86_64 kernel build, unsigned long is 64-bit and unsigned int and\nint are 32-bit wide. This setup causes the following mishap during the &=\n~VM_MERGEABLE assignment.\n\nVM_MERGEABLE is a 32-bit constant of type unsigned int, 0x8000'0000. \nAfter ~ is applied, it becomes 0x7fff'ffff unsigned int, which is then\npromoted to unsigned long before the & operation. This promotion fills\nupper 32 bits with leading 0s, as we're doing unsigned conversion (and\neven for a signed conversion, this wouldn't help as the leading bit is 0).\n& operation thus ends up AND-ing vm_flags with 0x0000'0000'7fff'ffff\ninstead of intended 0xffff'ffff'7fff'ffff and hence accidentally clears\nthe upper 32-bits of its value.\n\nFix it by changing `VM_MERGEABLE` constant to unsigned long, using the\nBIT() macro.\n\nNote: other VM_* flags are not affected: This only happens to the\nVM_MERGEABLE flag, as the other VM_* flags are all constants of type int\nand after ~ operation, they end up with leading 1 and are thus converted\nto unsigned long with leading 1s.\n\nNote 2:\nAfter commit 31defc3b01d9 (\"userfaultfd: remove (VM_)BUG_ON()s\"), this is\nno longer a kernel BUG, but a WARNING at the same place:\n\n[ 45.595973] WARNING: CPU: 1 PID: 2474 at mm/userfaultfd.c:2067\n\nbut the root-cause (flag-drop) remains the same.\n\n[akpm@linux-foundation.org: rust bindgen wasn't able to handle BIT(), from Miguel]"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["include/linux/mm.h", "rust/bindings/bindings_helper.h"], "versions": [{"version": "7677f7fd8be76659cd2d0db8ff4093bbb51c20e5", "lessThan": "41cb9fd904fe0c39d52e82dd84dc3c96b7aa9693", "status": "affected", "versionType": "git"}, {"version": "7677f7fd8be76659cd2d0db8ff4093bbb51c20e5", "lessThan": "92b82e232b8d8b116ac6e57aeae7a6033db92c60", "status": "affected", "versionType": "git"}, {"version": "7677f7fd8be76659cd2d0db8ff4093bbb51c20e5", "lessThan": "ac50c6e0a8f91a02b681af81abb2362fbb67cc18", "status": "affected", "versionType": "git"}, {"version": "7677f7fd8be76659cd2d0db8ff4093bbb51c20e5", "lessThan": "76385629f45740b7888f8fcd83bde955b10f61fe", "status": "affected", "versionType": "git"}, {"version": "7677f7fd8be76659cd2d0db8ff4093bbb51c20e5", "lessThan": "f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["include/linux/mm.h", "rust/bindings/bindings_helper.h"], "versions": [{"version": "5.13", "status": "affected"}, {"version": "0", "lessThan": "5.13", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.158", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.114", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.55", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17.3", "lessThanOrEqual": "6.17.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18-rc1", "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": "5.13", "versionEndExcluding": "6.1.158"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "6.6.114"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "6.12.55"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "6.17.3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "6.18-rc1"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/41cb9fd904fe0c39d52e82dd84dc3c96b7aa9693"}, {"url": "https://git.kernel.org/stable/c/92b82e232b8d8b116ac6e57aeae7a6033db92c60"}, {"url": "https://git.kernel.org/stable/c/ac50c6e0a8f91a02b681af81abb2362fbb67cc18"}, {"url": "https://git.kernel.org/stable/c/76385629f45740b7888f8fcd83bde955b10f61fe"}, {"url": "https://git.kernel.org/stable/c/f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93"}], "title": "mm/ksm: fix flag-dropping behavior in ksm_madvise", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/ksm: fix flag-dropping behavior in ksm_madvise\n\nsyzkaller discovered the following crash: (kernel BUG)\n\n[ 44.607039] ------------[ cut here ]------------\n[ 44.607422] kernel BUG at mm/userfaultfd.c:2067!\n[ 44.608148] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted 6.16.0-rc6 #1 PREEMPT(none)\n[ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[ 44.610695] RIP: 0010:userfaultfd_release_all+0x3a8/0x460\n\n<snip other registers, drop unreliable trace>\n\n[ 44.617726] Call Trace:\n[ 44.617926] <TASK>\n[ 44.619284] userfaultfd_release+0xef/0x1b0\n[ 44.620976] __fput+0x3f9/0xb60\n[ 44.621240] fput_close_sync+0x110/0x210\n[ 44.622222] __x64_sys_close+0x8f/0x120\n[ 44.622530] do_syscall_64+0x5b/0x2f0\n[ 44.622840] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[ 44.623244] RIP: 0033:0x7f365bb3f227\n\nKernel panics because it detects UFFD inconsistency during\nuserfaultfd_release_all(). Specifically, a VMA which has a valid pointer\nto vma->vm_userfaultfd_ctx, but no UFFD flags in vma->vm_flags.\n\nThe inconsistency is caused in ksm_madvise(): when user calls madvise()\nwith MADV_UNMEARGEABLE on a VMA that is registered for UFFD in MINOR mode,\nit accidentally clears all flags stored in the upper 32 bits of\nvma->vm_flags.\n\nAssuming x86_64 kernel build, unsigned long is 64-bit and unsigned int and\nint are 32-bit wide. This setup causes the following mishap during the &=\n~VM_MERGEABLE assignment.\n\nVM_MERGEABLE is a 32-bit constant of type unsigned int, 0x8000'0000. \nAfter ~ is applied, it becomes 0x7fff'ffff unsigned int, which is then\npromoted to unsigned long before the & operation. This promotion fills\nupper 32 bits with leading 0s, as we're doing unsigned conversion (and\neven for a signed conversion, this wouldn't help as the leading bit is 0).\n& operation thus ends up AND-ing vm_flags with 0x0000'0000'7fff'ffff\ninstead of intended 0xffff'ffff'7fff'ffff and hence accidentally clears\nthe upper 32-bits of its value.\n\nFix it by changing `VM_MERGEABLE` constant to unsigned long, using the\nBIT() macro.\n\nNote: other VM_* flags are not affected: This only happens to the\nVM_MERGEABLE flag, as the other VM_* flags are all constants of type int\nand after ~ operation, they end up with leading 1 and are thus converted\nto unsigned long with leading 1s.\n\nNote 2:\nAfter commit 31defc3b01d9 (\"userfaultfd: remove (VM_)BUG_ON()s\"), this is\nno longer a kernel BUG, but a WARNING at the same place:\n\n[ 45.595973] WARNING: CPU: 1 PID: 2474 at mm/userfaultfd.c:2067\n\nbut the root-cause (flag-drop) remains the same.\n\n[akpm@linux-foundation.org: rust bindgen wasn't able to handle BIT(), from Miguel]"}], "id": "CVE-2025-40040", "lastModified": "2025-10-30T15:05:32.197", "metrics": {}, "published": "2025-10-28T12:15:37.967", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/41cb9fd904fe0c39d52e82dd84dc3c96b7aa9693"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/76385629f45740b7888f8fcd83bde955b10f61fe"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/92b82e232b8d8b116ac6e57aeae7a6033db92c60"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ac50c6e0a8f91a02b681af81abb2362fbb67cc18"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"bugzilla": {"description": "kernel: mm/ksm: fix flag-dropping behavior in ksm_madvise", "id": "2406730", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2406730"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-40040", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-10-28T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-40040\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-40040\nhttps://lore.kernel.org/linux-cve-announce/2025102812-CVE-2025-40040-943a@gregkh/T"], "threat_severity": "Moderate"}