CVE-2026-93275
Received
Received - Intake
Race Condition in Linux Kernel Intel PT
Vulnerability report for CVE-2026-93275, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-24
Last updated on: 2026-09-24
Assigner: kernel.org
Description
Description
In 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.
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
