161 lines
10 KiB
JSON
161 lines
10 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2025-38554",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2025-04-16T04:51:24.025Z",
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"datePublished": "2025-08-19T17:02:33.315Z",
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"dateUpdated": "2026-08-05T12:02:52.067Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T12:02:52.067Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: fix a UAF when vma->mm is freed after vma->vm_refcnt got dropped\n\nBy inducing delays in the right places, Jann Horn created a reproducer for\na hard to hit UAF issue that became possible after VMAs were allowed to be\nrecycled by adding SLAB_TYPESAFE_BY_RCU to their cache.\n\nRace description is borrowed from Jann's discovery report:\nlock_vma_under_rcu() looks up a VMA locklessly with mas_walk() under\nrcu_read_lock(). At that point, the VMA may be concurrently freed, and it\ncan be recycled by another process. vma_start_read() then increments the\nvma->vm_refcnt (if it is in an acceptable range), and if this succeeds,\nvma_start_read() can return a recycled VMA.\n\nIn this scenario where the VMA has been recycled, lock_vma_under_rcu()\nwill then detect the mismatching ->vm_mm pointer and drop the VMA through\nvma_end_read(), which calls vma_refcount_put(). vma_refcount_put() drops\nthe refcount and then calls rcuwait_wake_up() using a copy of vma->vm_mm. \nThis is wrong: It implicitly assumes that the caller is keeping the VMA's\nmm alive, but in this scenario the caller has no relation to the VMA's mm,\nso the rcuwait_wake_up() can cause UAF.\n\nThe diagram depicting the race:\nT1 T2 T3\n== == ==\nlock_vma_under_rcu\n mas_walk\n <VMA gets removed from mm>\n mmap\n <the same VMA is reallocated>\n vma_start_read\n __refcount_inc_not_zero_limited_acquire\n munmap\n __vma_enter_locked\n refcount_add_not_zero\n vma_end_read\n vma_refcount_put\n __refcount_dec_and_test\n rcuwait_wait_event\n <finish operation>\n rcuwait_wake_up [UAF]\n\nNote that rcuwait_wait_event() in T3 does not block because refcount was\nalready dropped by T1. At this point T3 can exit and free the mm causing\nUAF in T1.\n\nTo avoid this we move vma->vm_mm verification into vma_start_read() and\ngrab vma->vm_mm to stabilize it before vma_refcount_put() operation.\n\n[surenb@google.com: v3]"
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The vulnerable path is entered from the architecture user page-fault handler (`lock_vma_under_rcu()`), `madvise()`/`userfaultfd`/`process_vm` paths, and `/proc/pid/maps` traversal — all require local code execution. No remote peer can drive the mmap/munmap/exit sequence needed for the race.\nAC:L - The attacker controls every side of the race — the page-faulting thread, the thread unmapping the VMA, and the second process that recycles the VMA slab object and then exits to free its mm — and can spray VMA allocations and retry the loop indefinitely across CPUs. Although the window is narrow, no condition lies outside the attacker's influence.\nPR:L - Any unprivileged local process can reach the code simply by taking a page fault or reading `/proc/pid/maps`; no capability, namespace privilege, or configuration gate exists on the path.\nUI:N - The attacker drives the entire sequence with its own threads and child processes; no victim action is required.\nS:U - The use-after-free corrupts kernel memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The freed `mm_struct` is read after being returned to `mm_cachep` and potentially reallocated, and the resulting UAF on a core mm object combined with the `wake_up_process()` primitive gives the attacker a path to arbitrary kernel memory disclosure.\nI:H - `rcuwait_wake_up()` loads a `task_struct *` out of freed, attacker-groomable memory and passes it to `wake_up_process()`, which writes into that object and dispatches through `p->sched_class->enqueue_task()` — an attacker-controlled indirect call yielding arbitrary write and control-flow hijack.\nA:H - Even without successful grooming, dereferencing a freed `mm_struct` and waking a bogus task pointer corrupts scheduler state and causes a kernel oops or panic, and the race can be retried in a loop."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"include/linux/mmap_lock.h",
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"mm/mmap_lock.c"
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],
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"versions": [
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{
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"version": "3104138517fc66aad21f4a2487bb572e9fc2e3ec",
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"lessThan": "6e88fe54721dee17d3496bc998f0c7d243896348",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "3104138517fc66aad21f4a2487bb572e9fc2e3ec",
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"lessThan": "1bcd236a2536a451e385f8d6d2bb589689ec812f",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "3104138517fc66aad21f4a2487bb572e9fc2e3ec",
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"lessThan": "9bbffee67ffd16360179327b57f3b1245579ef08",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"include/linux/mmap_lock.h",
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"mm/mmap_lock.c"
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],
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"versions": [
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{
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"version": "6.15",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.15",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.15.10",
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"lessThanOrEqual": "6.15.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.16.1",
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"lessThanOrEqual": "6.16.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.17",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.15",
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"versionEndExcluding": "6.15.10"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.15",
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"versionEndExcluding": "6.16.1"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.15",
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"versionEndExcluding": "6.17"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/6e88fe54721dee17d3496bc998f0c7d243896348"
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},
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{
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"url": "https://git.kernel.org/stable/c/1bcd236a2536a451e385f8d6d2bb589689ec812f"
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},
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{
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"url": "https://git.kernel.org/stable/c/9bbffee67ffd16360179327b57f3b1245579ef08"
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}
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],
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"title": "mm: fix a UAF when vma->mm is freed after vma->vm_refcnt got dropped",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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} |