GHSA-6574-VQV8-9334
Vulnerability from github – Published: 2025-01-06 18:31 – Updated: 2025-11-03 21:32In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix use-after-free when COWing tree bock and tracing is enabled
When a COWing a tree block, at btrfs_cow_block(), and we have the tracepoint trace_btrfs_cow_block() enabled and preemption is also enabled (CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extent buffer while inside the tracepoint code. This is because in some paths that call btrfs_cow_block(), such as btrfs_search_slot(), we are holding the last reference on the extent buffer @buf so btrfs_force_cow_block() drops the last reference on the @buf extent buffer when it calls free_extent_buffer_stale(buf), which schedules the release of the extent buffer with RCU. This means that if we are on a kernel with preemption, the current task may be preempted before calling trace_btrfs_cow_block() and the extent buffer already released by the time trace_btrfs_cow_block() is called, resulting in a use-after-free.
Fix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() to btrfs_force_cow_block() before the COWed extent buffer is freed. This also has a side effect of invoking the tracepoint in the tree defrag code, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() is called there, but this is fine and it was actually missing there.
{
"affected": [],
"aliases": [
"CVE-2024-56759"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-01-06T17:15:40Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free when COWing tree bock and tracing is enabled\n\nWhen a COWing a tree block, at btrfs_cow_block(), and we have the\ntracepoint trace_btrfs_cow_block() enabled and preemption is also enabled\n(CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extent\nbuffer while inside the tracepoint code. This is because in some paths\nthat call btrfs_cow_block(), such as btrfs_search_slot(), we are holding\nthe last reference on the extent buffer @buf so btrfs_force_cow_block()\ndrops the last reference on the @buf extent buffer when it calls\nfree_extent_buffer_stale(buf), which schedules the release of the extent\nbuffer with RCU. This means that if we are on a kernel with preemption,\nthe current task may be preempted before calling trace_btrfs_cow_block()\nand the extent buffer already released by the time trace_btrfs_cow_block()\nis called, resulting in a use-after-free.\n\nFix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() to\nbtrfs_force_cow_block() before the COWed extent buffer is freed.\nThis also has a side effect of invoking the tracepoint in the tree defrag\ncode, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() is\ncalled there, but this is fine and it was actually missing there.",
"id": "GHSA-6574-vqv8-9334",
"modified": "2025-11-03T21:32:03Z",
"published": "2025-01-06T18:31:03Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-56759"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/44f52bbe96dfdbe4aca3818a2534520082a07040"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/526ff5b27f090fb15040471f892cd2c9899ce314"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/66376f1a73cba57fd0af2631d7888605b738e499"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9a466b8693b9add05de99af00c7bdff8259ecf19"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba5120a2fb5f23b4d39d302e181aa5d4e28a90d1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c3a403d8ce36f5a809a492581de5ad17843e4701"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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