GHSA-XVMJ-27R5-9623
Vulnerability from github – Published: 2024-05-22 09:31 – Updated: 2024-05-22 09:31In the Linux kernel, the following vulnerability has been resolved:
cgroup: Fix memory leak caused by missing cgroup_bpf_offline
When enabling CONFIG_CGROUP_BPF, kmemleak can be observed by running the command as below:
$mount -t cgroup -o none,name=foo cgroup cgroup/
$umount cgroup/
unreferenced object 0xc3585c40 (size 64): comm "mount", pid 425, jiffies 4294959825 (age 31.990s) hex dump (first 32 bytes): 01 00 00 80 84 8c 28 c0 00 00 00 00 00 00 00 00 ......(......... 00 00 00 00 00 00 00 00 6c 43 a0 c3 00 00 00 00 ........lC...... backtrace: [] cgroup_bpf_inherit+0x44/0x24c [<1f03679c>] cgroup_setup_root+0x174/0x37c [] cgroup1_get_tree+0x2c0/0x4a0 [] vfs_get_tree+0x24/0x108 [] path_mount+0x384/0x988 [] do_mount+0x64/0x9c [<208c9cfe>] sys_mount+0xfc/0x1f4 [<06dd06e0>] ret_fast_syscall+0x0/0x48 [] 0xbeb4daa8
This is because that since the commit 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path") root_cgrp->bpf.refcnt.data is allocated by the function percpu_ref_init in cgroup_bpf_inherit which is called by cgroup_setup_root when mounting, but not freed along with root_cgrp when umounting. Adding cgroup_bpf_offline which calls percpu_ref_kill to cgroup_kill_sb can free root_cgrp->bpf.refcnt.data in umount path.
This patch also fixes the commit 4bfc0bb2c60e ("bpf: decouple the lifetime of cgroup_bpf from cgroup itself"). A cgroup_bpf_offline is needed to do a cleanup that frees the resources which are allocated by cgroup_bpf_inherit in cgroup_setup_root.
And inside cgroup_bpf_offline, cgroup_get() is at the beginning and cgroup_put is at the end of cgroup_bpf_release which is called by cgroup_bpf_offline. So cgroup_bpf_offline can keep the balance of cgroup's refcount.
{
"affected": [],
"aliases": [
"CVE-2021-47488"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-22T09:15:10Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncgroup: Fix memory leak caused by missing cgroup_bpf_offline\n\nWhen enabling CONFIG_CGROUP_BPF, kmemleak can be observed by running\nthe command as below:\n\n $mount -t cgroup -o none,name=foo cgroup cgroup/\n $umount cgroup/\n\nunreferenced object 0xc3585c40 (size 64):\n comm \"mount\", pid 425, jiffies 4294959825 (age 31.990s)\n hex dump (first 32 bytes):\n 01 00 00 80 84 8c 28 c0 00 00 00 00 00 00 00 00 ......(.........\n 00 00 00 00 00 00 00 00 6c 43 a0 c3 00 00 00 00 ........lC......\n backtrace:\n [\u003ce95a2f9e\u003e] cgroup_bpf_inherit+0x44/0x24c\n [\u003c1f03679c\u003e] cgroup_setup_root+0x174/0x37c\n [\u003ced4b0ac5\u003e] cgroup1_get_tree+0x2c0/0x4a0\n [\u003cf85b12fd\u003e] vfs_get_tree+0x24/0x108\n [\u003cf55aec5c\u003e] path_mount+0x384/0x988\n [\u003ce2d5e9cd\u003e] do_mount+0x64/0x9c\n [\u003c208c9cfe\u003e] sys_mount+0xfc/0x1f4\n [\u003c06dd06e0\u003e] ret_fast_syscall+0x0/0x48\n [\u003ca8308cb3\u003e] 0xbeb4daa8\n\nThis is because that since the commit 2b0d3d3e4fcf (\"percpu_ref: reduce\nmemory footprint of percpu_ref in fast path\") root_cgrp-\u003ebpf.refcnt.data\nis allocated by the function percpu_ref_init in cgroup_bpf_inherit which\nis called by cgroup_setup_root when mounting, but not freed along with\nroot_cgrp when umounting. Adding cgroup_bpf_offline which calls\npercpu_ref_kill to cgroup_kill_sb can free root_cgrp-\u003ebpf.refcnt.data in\numount path.\n\nThis patch also fixes the commit 4bfc0bb2c60e (\"bpf: decouple the lifetime\nof cgroup_bpf from cgroup itself\"). A cgroup_bpf_offline is needed to do a\ncleanup that frees the resources which are allocated by cgroup_bpf_inherit\nin cgroup_setup_root.\n\nAnd inside cgroup_bpf_offline, cgroup_get() is at the beginning and\ncgroup_put is at the end of cgroup_bpf_release which is called by\ncgroup_bpf_offline. So cgroup_bpf_offline can keep the balance of\ncgroup\u0027s refcount.",
"id": "GHSA-xvmj-27r5-9623",
"modified": "2024-05-22T09:31:46Z",
"published": "2024-05-22T09:31:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47488"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/01599bf7cc2b49c3d2be886cb438647dc25446ed"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/04f8ef5643bcd8bcde25dfdebef998aea480b2ba"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b529f88d93884cf8ccafda793ee3d27b82fa578d"
}
],
"schema_version": "1.4.0",
"severity": []
}
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