| { |
| "containers": { |
| "cna": { |
| "providerMetadata": { |
| "orgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038" |
| }, |
| "descriptions": [ |
| { |
| "lang": "en", |
| "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: PPC: Book3S HV: Fix stack handling in idle_kvm_start_guest()\n\nIn commit 10d91611f426 (\"powerpc/64s: Reimplement book3s idle code in\nC\") kvm_start_guest() became idle_kvm_start_guest(). The old code\nallocated a stack frame on the emergency stack, but didn't use the\nframe to store anything, and also didn't store anything in its caller's\nframe.\n\nidle_kvm_start_guest() on the other hand is written more like a normal C\nfunction, it creates a frame on entry, and also stores CR/LR into its\ncallers frame (per the ABI). The problem is that there is no caller\nframe on the emergency stack.\n\nThe emergency stack for a given CPU is allocated with:\n\n paca_ptrs[i]->emergency_sp = alloc_stack(limit, i) + THREAD_SIZE;\n\nSo emergency_sp actually points to the first address above the emergency\nstack allocation for a given CPU, we must not store above it without\nfirst decrementing it to create a frame. This is different to the\nregular kernel stack, paca->kstack, which is initialised to point at an\ninitial frame that is ready to use.\n\nidle_kvm_start_guest() stores the backchain, CR and LR all of which\nwrite outside the allocation for the emergency stack. It then creates a\nstack frame and saves the non-volatile registers. Unfortunately the\nframe it creates is not large enough to fit the non-volatiles, and so\nthe saving of the non-volatile registers also writes outside the\nemergency stack allocation.\n\nThe end result is that we corrupt whatever is at 0-24 bytes, and 112-248\nbytes above the emergency stack allocation.\n\nIn practice this has gone unnoticed because the memory immediately above\nthe emergency stack happens to be used for other stack allocations,\neither another CPUs mc_emergency_sp or an IRQ stack. See the order of\ncalls to irqstack_early_init() and emergency_stack_init().\n\nThe low addresses of another stack are the top of that stack, and so are\nonly used if that stack is under extreme pressue, which essentially\nnever happens in practice - and if it did there's a high likelyhood we'd\ncrash due to that stack overflowing.\n\nStill, we shouldn't be corrupting someone else's stack, and it is purely\nluck that we aren't corrupting something else.\n\nTo fix it we save CR/LR into the caller's frame using the existing r1 on\nentry, we then create a SWITCH_FRAME_SIZE frame (which has space for\npt_regs) on the emergency stack with the backchain pointing to the\nexisting stack, and then finally we switch to the new frame on the\nemergency stack." |
| } |
| ], |
| "affected": [ |
| { |
| "product": "Linux", |
| "vendor": "Linux", |
| "defaultStatus": "unaffected", |
| "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", |
| "programFiles": [ |
| "arch/powerpc/kvm/book3s_hv_rmhandlers.S" |
| ], |
| "versions": [ |
| { |
| "version": "10d91611f426d4bafd2a83d966c36da811b2f7ad", |
| "lessThan": "80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7", |
| "status": "affected", |
| "versionType": "git" |
| }, |
| { |
| "version": "10d91611f426d4bafd2a83d966c36da811b2f7ad", |
| "lessThan": "fbd724c49bead048ae9fc1a5b7bff2fb3e54f855", |
| "status": "affected", |
| "versionType": "git" |
| }, |
| { |
| "version": "10d91611f426d4bafd2a83d966c36da811b2f7ad", |
| "lessThan": "6d077c37c4643394b1bae9682da48164fc147ea8", |
| "status": "affected", |
| "versionType": "git" |
| }, |
| { |
| "version": "10d91611f426d4bafd2a83d966c36da811b2f7ad", |
| "lessThan": "9b4416c5095c20e110c82ae602c254099b83b72f", |
| "status": "affected", |
| "versionType": "git" |
| } |
| ] |
| }, |
| { |
| "product": "Linux", |
| "vendor": "Linux", |
| "defaultStatus": "affected", |
| "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", |
| "programFiles": [ |
| "arch/powerpc/kvm/book3s_hv_rmhandlers.S" |
| ], |
| "versions": [ |
| { |
| "version": "5.2", |
| "status": "affected" |
| }, |
| { |
| "version": "0", |
| "lessThan": "5.2", |
| "status": "unaffected", |
| "versionType": "semver" |
| }, |
| { |
| "version": "5.4.156", |
| "lessThanOrEqual": "5.4.*", |
| "status": "unaffected", |
| "versionType": "semver" |
| }, |
| { |
| "version": "5.10.76", |
| "lessThanOrEqual": "5.10.*", |
| "status": "unaffected", |
| "versionType": "semver" |
| }, |
| { |
| "version": "5.14.15", |
| "lessThanOrEqual": "5.14.*", |
| "status": "unaffected", |
| "versionType": "semver" |
| }, |
| { |
| "version": "5.15", |
| "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": "5.2", |
| "versionEndExcluding": "5.4.156" |
| }, |
| { |
| "vulnerable": true, |
| "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", |
| "versionStartIncluding": "5.2", |
| "versionEndExcluding": "5.10.76" |
| }, |
| { |
| "vulnerable": true, |
| "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", |
| "versionStartIncluding": "5.2", |
| "versionEndExcluding": "5.14.15" |
| }, |
| { |
| "vulnerable": true, |
| "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", |
| "versionStartIncluding": "5.2", |
| "versionEndExcluding": "5.15" |
| } |
| ] |
| } |
| ] |
| } |
| ], |
| "references": [ |
| { |
| "url": "https://git.kernel.org/stable/c/80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7" |
| }, |
| { |
| "url": "https://git.kernel.org/stable/c/fbd724c49bead048ae9fc1a5b7bff2fb3e54f855" |
| }, |
| { |
| "url": "https://git.kernel.org/stable/c/6d077c37c4643394b1bae9682da48164fc147ea8" |
| }, |
| { |
| "url": "https://git.kernel.org/stable/c/9b4416c5095c20e110c82ae602c254099b83b72f" |
| } |
| ], |
| "title": "KVM: PPC: Book3S HV: Fix stack handling in idle_kvm_start_guest()", |
| "x_generator": { |
| "engine": "bippy-1.2.0" |
| } |
| } |
| }, |
| "cveMetadata": { |
| "assignerOrgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038", |
| "cveID": "CVE-2021-47465", |
| "requesterUserId": "gregkh@kernel.org", |
| "serial": "1", |
| "state": "PUBLISHED" |
| }, |
| "dataType": "CVE_RECORD", |
| "dataVersion": "5.0" |
| } |
