180 lines
11 KiB
JSON
180 lines
11 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-2026-98982",
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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": "2026-09-25T10:25:14.384Z",
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"datePublished": "2026-10-23T12:19:59.784Z",
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"dateUpdated": "2026-10-24T14:09:50.745Z"
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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": "2026-10-24T14:09:50.745Z"
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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\nnamespace: don't let a pseudo dentry become the root of a mount\n\nd_alloc_pseudo() hands out dentries for pipes, sockets and other files\nthat are never anyone's child or parent. They carry DCACHE_NORCU and\ndentry_free() frees them right away because no lockless path walk can\never reach them. That holds as long as such a dentry isn't the root of\na mount. But bind mounting /proc/self/fd/<fd> of such a file does\nexactly that.\n\nMost callers of alloc_file_pseudo() put their files on kernel-internal\nmounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It\nplaces the token file on the bpffs mount the caller handed it and that\nmount is in the caller's mount namespace so the clone goes through:\n\n mount --bind /proc/self/fd/<token> <file>\n open_tree(tokfd, \"\", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount()\n\n__follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq\nand d_flags of the dentry and only then checks mount_lock. The dentry\ncan be gone by then. The final mntput() of an unmounted parent unhooks\na child that stayed attached to it under mount_lock alone. When the\nchild's holder does the final put right after that the root is dput()\nand freed immediately while a walker that found the mount hashed still\nlooks at it.\n\nRefuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing\nsensible can be done with a bind mount of a bpf token anyway."
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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 - Local bpf(BPF_TOKEN_CREATE) reaches bpf_token_create()/alloc_file_pseudo(), after which mount(MS_BIND) or open_tree(OPEN_TREE_CLONE) reaches the patched __do_loopback() on /proc/self/fd/<token>; no network protocol carries the triggering data.\nAC:L - The attacker controls creation and teardown of the token-root mount and can race cleanup_mnt()/dput() against openat() reaching __follow_mount_rcu() using concurrent threads; neither side of the race requires external timing or victim-controlled state.\nPR:L - bpf_token_create() requires CAP_BPF in the bpffs user namespace, while open_tree(OPEN_TREE_CLONE) and move_mount() require CAP_SYS_ADMIN over the mount namespace; because bpf_fs_type has FS_USERNS_MOUNT, an ordinary user can obtain these capabilities through unprivileged user and mount namespaces.\nUI:N - The attacking process performs every required action itself: mounting delegated bpffs, creating the token, cloning and tearing down mounts, and racing openat(); no victim must mount, open, or otherwise process attacker-supplied data.\nS:U - The freed dentry is consumed by __follow_mount_rcu() inside the same host kernel, yielding ordinary local kernel compromise or denial of service rather than crossing a VM, IOMMU, or separate security-authority boundary.\nC:H - cleanup_mnt() can dput() and immediately free the DCACHE_NORCU mount root while __follow_mount_rcu() still reads its d_seq, d_flags, and potentially d_op; attacker-driven dentry-cache reuse makes this kernel UAF capable of high-impact memory disclosure.\nI:H - The freed struct dentry can be reclaimed through attacker-driven dentry allocation, letting heap spraying influence fields and the d_op->d_manage dispatch consumed by __follow_mount_rcu(); this is an exploitable kernel UAF path to arbitrary modification or control-flow hijacking.\nA:H - __follow_mount_rcu() dereferences the mount root after dentry_free() has returned it immediately to dentry_cache, so poisoned or reclaimed contents can cause a kernel oops or panic, and attacker-controlled threads can repeat the race."
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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/namespace.c"
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],
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"versions": [
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{
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"version": "35f96de04127d332a5c5e8a155d31f452f88c76d",
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"lessThan": "a256e31e0c54c4c37d2523aa52faabdcdd2ebc07",
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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": "35f96de04127d332a5c5e8a155d31f452f88c76d",
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"lessThan": "7e1c466011ba9e64d43075396badc03191bcee44",
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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": "35f96de04127d332a5c5e8a155d31f452f88c76d",
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"lessThan": "00287afa7cd989efdbf5822b7efac33cce7d489a",
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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": "35f96de04127d332a5c5e8a155d31f452f88c76d",
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"lessThan": "b138e16fb1e81376cea89f727dda7bfccd140de4",
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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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"fs/namespace.c"
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],
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"versions": [
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{
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"version": "6.9",
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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": "6.9",
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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": "6.12.113",
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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": "6.18.57",
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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": "7.2.11",
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"lessThanOrEqual": "7.2.*",
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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": "7.3",
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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": "6.9",
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"versionEndExcluding": "6.12.113"
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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": "6.9",
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"versionEndExcluding": "6.18.57"
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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": "6.9",
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"versionEndExcluding": "7.2.11"
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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": "6.9",
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"versionEndExcluding": "7.3"
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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/a256e31e0c54c4c37d2523aa52faabdcdd2ebc07"
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},
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{
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"url": "https://git.kernel.org/stable/c/7e1c466011ba9e64d43075396badc03191bcee44"
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},
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{
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"url": "https://git.kernel.org/stable/c/00287afa7cd989efdbf5822b7efac33cce7d489a"
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},
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{
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"url": "https://git.kernel.org/stable/c/b138e16fb1e81376cea89f727dda7bfccd140de4"
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}
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],
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"title": "namespace: don't let a pseudo dentry become the root of a mount",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |