mirror of
https://github.com/CVEProject/cvelist.git
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124 lines
8.0 KiB
JSON
124 lines
8.0 KiB
JSON
{
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"data_version": "4.0",
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"data_type": "CVE",
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"data_format": "MITRE",
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"CVE_data_meta": {
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"ID": "CVE-2021-47465",
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"ASSIGNER": "cve@kernel.org",
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"STATE": "PUBLIC"
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},
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"description": {
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"description_data": [
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{
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"lang": "eng",
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"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."
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}
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]
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},
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"problemtype": {
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"problemtype_data": [
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{
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"description": [
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{
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"lang": "eng",
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"value": "n/a"
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}
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]
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}
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]
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},
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"affects": {
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"vendor": {
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"vendor_data": [
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{
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"vendor_name": "Linux",
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"product": {
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"product_data": [
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{
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"product_name": "Linux",
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"version": {
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"version_data": [
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{
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"version_affected": "<",
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"version_name": "10d91611f426",
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"version_value": "80bbb0bc3a02"
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},
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{
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"version_value": "not down converted",
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"x_cve_json_5_version_data": {
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"versions": [
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{
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"version": "5.2",
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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": "5.2",
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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": "5.4.156",
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"lessThanOrEqual": "5.4.*",
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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": "5.10.76",
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"lessThanOrEqual": "5.10.*",
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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": "5.14.15",
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"lessThanOrEqual": "5.14.*",
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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": "5.15",
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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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"defaultStatus": "affected"
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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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}
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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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"reference_data": [
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{
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"url": "https://git.kernel.org/stable/c/80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7",
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"refsource": "MISC",
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"name": "https://git.kernel.org/stable/c/80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7"
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},
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{
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"url": "https://git.kernel.org/stable/c/fbd724c49bead048ae9fc1a5b7bff2fb3e54f855",
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"refsource": "MISC",
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"name": "https://git.kernel.org/stable/c/fbd724c49bead048ae9fc1a5b7bff2fb3e54f855"
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},
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{
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"url": "https://git.kernel.org/stable/c/6d077c37c4643394b1bae9682da48164fc147ea8",
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"refsource": "MISC",
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"name": "https://git.kernel.org/stable/c/6d077c37c4643394b1bae9682da48164fc147ea8"
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},
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{
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"url": "https://git.kernel.org/stable/c/9b4416c5095c20e110c82ae602c254099b83b72f",
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"refsource": "MISC",
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"name": "https://git.kernel.org/stable/c/9b4416c5095c20e110c82ae602c254099b83b72f"
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}
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]
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},
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"generator": {
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"engine": "bippy-9e1c9544281a"
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}
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} |