GHSA-FRRX-CHJ7-RCHF
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()
In the beginning of the loop, we try to obtain a locked delayed ref head, if 'locked_ref' is currently NULL, by calling btrfs_select_ref_head(), which can return an error pointer. If the error pointer is -EAGAIN we do a continue and go back to the beginning of the loop, which will not try again to call btrfs_select_ref_head() since 'locked_ref' is no longer NULL but it's ERR_PTR(-EAGAIN), and then we do:
spin_lock(&locked_ref->lock);
against a ERR_PTR(-EAGAIN) value, generating an invalid pointer dereference.
Fix this by ensuring that 'locked_ref' is set to NULL when btrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing 'count' as well, to prevent infinite looping. We do this by doing a goto to the bottom of the loop that already sets 'locked_ref' to NULL and does a cond_resched(), with an increment to 'count' right before the goto. These measures were in place before the refactoring in commit 0110a4c43451 ("btrfs: refactor __btrfs_run_delayed_refs loop") but were unintentionally lost afterwards.
{
"affected": [],
"aliases": [
"CVE-2026-74321"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:32Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix invalid pointer dereference in __btrfs_run_delayed_refs()\n\nIn the beginning of the loop, we try to obtain a locked delayed ref head,\nif \u0027locked_ref\u0027 is currently NULL, by calling btrfs_select_ref_head(),\nwhich can return an error pointer. If the error pointer is -EAGAIN we do\na continue and go back to the beginning of the loop, which will not try\nagain to call btrfs_select_ref_head() since \u0027locked_ref\u0027 is no longer\nNULL but it\u0027s ERR_PTR(-EAGAIN), and then we do:\n\n spin_lock(\u0026locked_ref-\u003elock);\n\nagainst a ERR_PTR(-EAGAIN) value, generating an invalid pointer\ndereference.\n\nFix this by ensuring that \u0027locked_ref\u0027 is set to NULL when\nbtrfs_select_ref_head() returns ERR_PTR(-EAGAIN) and incrementing \u0027count\u0027\nas well, to prevent infinite looping. We do this by doing a goto to the\nbottom of the loop that already sets \u0027locked_ref\u0027 to NULL and does a\ncond_resched(), with an increment to \u0027count\u0027 right before the goto.\nThese measures were in place before the refactoring in commit 0110a4c43451\n(\"btrfs: refactor __btrfs_run_delayed_refs loop\") but were unintentionally\nlost afterwards.",
"id": "GHSA-frrx-chj7-rchf",
"modified": "2026-08-17T06:33:38Z",
"published": "2026-08-15T06:32:30Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74321"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/015dc4a1e0c2cba551d4620eba13d26d5081dc34"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3b15d02be05e74321adb1e0ae0cb4ccfba7c6cb1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/486f8298b6188ff11ef1f4be7f1d5d2e4d1b1fae"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/65770111a2d47c2b15e20b2ba92bb12198f289d4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9faa6b69ad73f03c7bde53e07d75a28822dc9a1a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a71143590ce9764dbcb47617647592ff8b4d48bc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba9fa2ff5981589bb49094d3358c339b37c47f53"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c372ca227e16bace86f1df1fa4ae6849e2fcfa28"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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