mm/ksm: fix flag-dropping behavior in ksm_madvise
In the Linux kernel, the following vulnerability has been resolved: mm/ksm: fix flag-dropping behavior in ksm_madvise syzkaller discovered the following crash: (kernel BUG) [ 44.607039] ------------[ cut here ]------------ [ 44.607422] kernel BUG at mm/userfaultfd.c:2067! [ 44.608148] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted 6.16.0-rc6 #1 PREEMPT(none) [ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.610695] RIP: 0010:userfaultfd_release_all+0x3a8/0x460 [ 44.617726] Call Trace: [ 44.617926] [ 44.619284] userfaultfd_release+0xef/0x1b0 [ 44.620976] __fput+0x3f9/0xb60 [ 44.621240] fput_close_sync+0x110/0x210 [ 44.622222] __x64_sys_close+0x8f/0x120 [ 44.622530] do_syscall_64+0x5b/0x2f0 [ 44.622840] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 44.623244] RIP: 0033:0x7f365bb3f227 Kernel panics because it detects UFFD inconsistency during userfaultfd_release_all(). Specifically, a VMA which has a valid pointer to vma->vm_userfaultfd_ctx, but no UFFD flags in vma->vm_flags. The inconsistency is caused in ksm_madvise(): when user calls madvise() with MADV_UNMEARGEABLE on a VMA that is registered for UFFD in MINOR mode, it accidentally clears all flags stored in the upper 32 bits of vma->vm_flags. Assuming x86_64 kernel build, unsigned long is 64-bit and unsigned int and int are 32-bit wide. This setup causes the fol
CVE-2025-40040
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-40040
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "850f1ea245bdc0ce6a3fd36bfb80d8cf9647cb71",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "788e5385d0ff69cdba1cabccb9dab8d9647b9239",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "b69f19244c2b6475c8a6eb72f0fb0d53509e48cd",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "41cb9fd904fe0c39d52e82dd84dc3c96b7aa9693",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "92b82e232b8d8b116ac6e57aeae7a6033db92c60",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "ac50c6e0a8f91a02b681af81abb2362fbb67cc18",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "76385629f45740b7888f8fcd83bde955b10f61fe",
"versionType": "git"
},
{
"status": "affected",
"version": "63c17fb8e5a46a16e10e82005748837fd11a2024",
"lessThan": "f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93",
"versionType": "git"
}
],
"programFiles": [
"include/linux/mm.h",
"rust/bindings/bindings_helper.h"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.6"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.4.302",
"versionType": "semver",
"lessThanOrEqual": "5.4.*"
},
{
"status": "unaffected",
"version": "5.10.247",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.197",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.158",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.114",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.55",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.17.3",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"include/linux/mm.h",
"rust/bindings/bindings_helper.h"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-40040
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #30667 · Revision 1
- Added to Heist Feed
- Publisher date