275 lines
15 KiB
JSON
275 lines
15 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-2026-93798",
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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": "2026-09-18T17:59:28.789Z",
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"datePublished": "2026-09-24T16:02:31.291Z",
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"dateUpdated": "2026-10-03T10:57:32.550Z"
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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": "2026-10-03T10:57:32.550Z"
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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\nbtrfs: fix reloc root cleanup in merge_reloc_roots()\n\nIf the root we got has zero root refs in its root item, we are resetting\nthe root's ->reloc_root without using barriers like we do everywhere else.\nSashiko complained about this while reviewing another patch, and it's\ncorrect (see the Link tag below).\n\nAlso, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless\nthe root points to the reloc root we have.\n\nFix this by using clear_reloc_root(), which issues the memory barrier\nafter setting the root's ->reloc_root to NULL and before clearing the bit\nBTRFS_ROOT_DEAD_RELOC_TREE from the root."
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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 - merge_reloc_roots() is reached from local VFS activity: unlink/write call btrfs_update_block_group() which btrfs_mark_bg_to_reclaim(); btrfs_reclaim_bgs_work() then runs btrfs_relocate_chunk()->btrfs_relocate_block_group()->relocate_block_group()->prepare_to_merge()->merge_reloc_roots(). No network protocol supplies the causing state.\nAC:L - When relocate_block_group() fails (the attacker can force ENOSPC via extra allocations), prepare_to_merge() leaves reloc roots at 0 refs and merge_reloc_roots() NULLs root->reloc_root then clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE) without smp_wmb(). Concurrent writes invoke btrfs_init_reloc_root()/have_reloc_root() on that same root, so the attacker drives both sides.\nPR:L - BTRFS_IOC_BALANCE requires capable(CAP_SYS_ADMIN), but btrfs_buffered_write() and unlink used to mark a block group reclaimable have no capability gate. btrfs_fs_type lacks FS_USERNS_MOUNT, so the volume is admin-mounted, yet any unprivileged uid with write permission on that mount can induce reclaim into merge_reloc_roots().\nUI:N - The attacker induces the 0-ref merge_reloc_roots() cleanup with their own writes and deletions on a btrfs they can already write, then races have_reloc_root() with further writes or btrfs_ioctl_snap_create(); no second user needs to mount an image or run balance.\nS:U - The use-after-free is of the struct btrfs_root stored in fs_root->reloc_root inside the same host kernel that mounted the volume; merge_reloc_roots() does not cross a VM, IOMMU, or sandbox authority.\nC:H - Missing smp_wmb() in merge_reloc_roots() lets have_reloc_root() see BTRFS_ROOT_DEAD_RELOC_TREE already clear while still loading the old root->reloc_root pointer; btrfs_should_ignore_reloc_root() then reads reloc_root->commit_root after the matching btrfs_put_root() dropped that reloc root.\nI:H - The same stale reloc_root is written by btrfs_init_reloc_root() via btrfs_set_root_last_trans() and by commit_fs_roots()->btrfs_update_reloc_root() which mutates reloc_root->root_item, giving a write-after-free of struct btrfs_root.\nA:H - Using the dangling reloc_root after merge_reloc_roots()'s btrfs_put_root() oopses; if clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE) becomes visible while the pointer still refers to the 0-ref tree, btrfs_reloc_pre_snapshot() hits BUG_ON(btrfs_root_refs(&root->root_item)==0)."
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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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"fs/btrfs/relocation.c"
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],
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"versions": [
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{
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"version": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "29531470b1bf1e8bd2df4941fe913106edbca615",
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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": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "415f8665a969d3c906e4fd7c90fcbb4b357886f6",
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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": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "ee695a968aa73b1e67ccbf2133dc0e54381d32b2",
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"status": "affected",
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},
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{
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"lessThan": "0bc25f0a2d1b3e0a691431c4d7aef36afcd527c5",
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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": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "ab48583aa9948205ff9a6470e23dbff74c565e24",
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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": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "63d6b1f04cd91c825329712aa526215ffa5d11ca",
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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": "1dae7e0e58b484eaa43d530f211098fdeeb0f404",
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"lessThan": "b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8",
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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": "ee08663380ffd5a45a1c87580fbc305e8413c235",
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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": "33823378ff2b510fd7b566f25bb18438aeb9b23b",
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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": "5.4.54",
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"lessThan": "5.5",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "5.7.11",
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"lessThan": "5.8",
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"status": "affected",
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"versionType": "semver"
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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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"fs/btrfs/relocation.c"
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],
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"versions": [
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{
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"version": "5.8",
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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": "5.8",
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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": "5.10.271",
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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": "5.15.222",
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"lessThanOrEqual": "5.15.*",
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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": "6.1.189",
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"lessThanOrEqual": "6.1.*",
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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": "6.6.158",
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"lessThanOrEqual": "6.6.*",
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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": "6.12.111",
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"lessThanOrEqual": "6.12.*",
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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": "6.18.53",
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"lessThanOrEqual": "6.18.*",
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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": "7.2",
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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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"nodes": [
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"operator": "OR",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "5.8",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/29531470b1bf1e8bd2df4941fe913106edbca615"
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},
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{
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"url": "https://git.kernel.org/stable/c/415f8665a969d3c906e4fd7c90fcbb4b357886f6"
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},
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{
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"url": "https://git.kernel.org/stable/c/ee695a968aa73b1e67ccbf2133dc0e54381d32b2"
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},
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{
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"url": "https://git.kernel.org/stable/c/0bc25f0a2d1b3e0a691431c4d7aef36afcd527c5"
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},
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{
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"url": "https://git.kernel.org/stable/c/ab48583aa9948205ff9a6470e23dbff74c565e24"
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},
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{
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"url": "https://git.kernel.org/stable/c/63d6b1f04cd91c825329712aa526215ffa5d11ca"
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},
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{
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"url": "https://git.kernel.org/stable/c/b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8"
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}
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],
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"title": "btrfs: fix reloc root cleanup in merge_reloc_roots()",
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"x_generator": {
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} |