GHSA-J5V2-XWXQ-RP3V
Vulnerability from github – Published: 2026-09-24 18:31 – Updated: 2026-09-24 18:31In the Linux kernel, the following vulnerability has been resolved:
perf/x86/intel/pt: Fix stop/start with no update
If pt_event_stop() is called without PERF_EF_UPDATE flag, then perf_aux_output_end() is not called. A subsequent call to pt_event_start() will call perf_aux_output_begin() again which violates the rule against nesting and triggers a WARNING in perf_aux_output_begin().
Originally, pt_event_stop() was never called without PERF_EF_UPDATE, because the only code paths to do so are from event overflow, and Intel PT does not do that.
However the introduction of group throttling by commit 9734e25fbf5ae ("perf: Fix the throttle logic for a group") meant that an Intel PT event could be throttled if it was part of a group. Throttling calls PMU ->stop() / ->start() callbacks without flags.
An example is when AUX area sampling is used. The following commands hit the issue:
echo 10000 > /proc/sys/kernel/perf_event_max_sample_rate
perf record -F32000 --aux-sample -e '{intel_pt//u,cycles:u}' \
-- bash -c 'for i in seq 1 100000 ; do true ; done'
Use PERF_HES_UPTODATE to track whether perf_aux_output_begin() and perf_aux_output_end() are balanced. A cleared PERF_HES_UPTODATE bit indicates that an AUX output context is still open.
Amend pt_event_start() / pt_event_stop() accordingly so that begin/end stay balanced:
-
In non-snapshot mode, stop() always closes the buffer (the buffer may have run out of space, and that accounting is done by the update), so a following start() opens a fresh one as before.
-
In snapshot/overwrite mode, stop() without PERF_EF_UPDATE leaves the buffer open so that pt_event_snapshot_aux() can still copy from it, and start() then only re-enables tracing instead of calling perf_aux_output_begin() again.
Note that pt_event_del() calls pt_event_stop() with PERF_EF_UPDATE flag set (as is required by the documentation), so a final call to perf_aux_output_end() is assured.
{
"affected": [],
"aliases": [
"CVE-2026-93275"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-24T16:17:24Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/x86/intel/pt: Fix stop/start with no update\n\nIf pt_event_stop() is called without PERF_EF_UPDATE flag, then\nperf_aux_output_end() is not called. A subsequent call to pt_event_start()\nwill call perf_aux_output_begin() again which violates the rule against\nnesting and triggers a WARNING in perf_aux_output_begin().\n\nOriginally, pt_event_stop() was never called without PERF_EF_UPDATE,\nbecause the only code paths to do so are from event overflow, and Intel PT\ndoes not do that.\n\nHowever the introduction of group throttling by commit 9734e25fbf5ae\n(\"perf: Fix the throttle logic for a group\") meant that an Intel PT event\ncould be throttled if it was part of a group. Throttling calls PMU\n -\u003estop() / -\u003estart() callbacks without flags.\n\nAn example is when AUX area sampling is used. The following commands\nhit the issue:\n\n echo 10000 \u003e /proc/sys/kernel/perf_event_max_sample_rate\n\n perf record -F32000 --aux-sample -e \u0027{intel_pt//u,cycles:u}\u0027 \\\n -- bash -c \u0027for i in `seq 1 100000` ; do true ; done\u0027\n\nUse PERF_HES_UPTODATE to track whether perf_aux_output_begin() and\nperf_aux_output_end() are balanced. A cleared PERF_HES_UPTODATE bit\nindicates that an AUX output context is still open.\n\nAmend pt_event_start() / pt_event_stop() accordingly so that begin/end\nstay balanced:\n\n - In non-snapshot mode, stop() always closes the buffer (the buffer may\n have run out of space, and that accounting is done by the update), so\n a following start() opens a fresh one as before.\n\n - In snapshot/overwrite mode, stop() without PERF_EF_UPDATE leaves the\n buffer open so that pt_event_snapshot_aux() can still copy from it,\n and start() then only re-enables tracing instead of calling\n perf_aux_output_begin() again.\n\nNote that pt_event_del() calls pt_event_stop() with PERF_EF_UPDATE flag set\n(as is required by the documentation), so a final call to\nperf_aux_output_end() is assured.",
"id": "GHSA-j5v2-xwxq-rp3v",
"modified": "2026-09-24T18:31:25Z",
"published": "2026-09-24T18:31:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93275"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2e17bf3a469a41457a3bc31b1f8fd66b6ce94a6d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/304844b5545f444d523286da8228a1cbc46ffffa"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9b919fb5512f256e9e0604faf960b2bb98aab454"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cab5015ee3f25f789b4a368f2abfa65536576b78"
}
],
"schema_version": "1.4.0",
"severity": []
}
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