# CVE-2026-43416: powerpc, perf: Check that current->mm is alive before getting user callchain

Status: published. Published: 2026-05-08. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

powerpc, perf: Check that current->mm is alive before getting user callchain

It may happen that mm is already released, which leads to kernel panic.
This adds the NULL check for current->mm, similarly to
commit 20afc60f892d ("x86, perf: Check that current->mm is alive before getting user callchain").

I was getting this panic when running a profiling BPF program
(profile.py from bcc-tools):

    [26215.051935] Kernel attempted to read user page (588) - exploit attempt? (uid: 0)
    [26215.051950] BUG: Kernel NULL pointer dereference on read at 0x00000588
    [26215.051952] Faulting instruction address: 0xc00000000020fac0
    [26215.051957] Oops: Kernel access of bad area, sig: 11 [#1]
    [...]
    [26215.052049] Call Trace:
    [26215.052050] [c000000061da6d30] [c00000000020fc10] perf_callchain_user_64+0x2d0/0x490 (unreliable)
    [26215.052054] [c000000061da6dc0] [c00000000020f92c] perf_callchain_user+0x1c/0x30
    [26215.052057] [c000000061da6de0] [c0000000005ab2a0] get_perf_callchain+0x100/0x360
    [26215.052063] [c000000061da6e70] [c000000000573bc8] bpf_get_stackid+0x88/0xf0
    [26215.052067] [c000000061da6ea0] [c008000000042258] bpf_prog_16d4ab9ab662f669_do_perf_event+0xf8/0x274
    [...]

In addition, move storing the top-level stack entry to generic
perf_callchain_user to make sure the top-evel entry is always captured,
even if current->mm is NULL.

[Maddy: fixed message to avoid checkpatch format style error]

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 20002ded4d937ca87aca6253b874920a96a763c4; < 98074e16742ae87fb82e234b419783c5ffc9baea (affected, git); ≥ 20002ded4d937ca87aca6253b874920a96a763c4; < 7e5f60b8cfc02a2b23a40a5f5fd2fa81d010e737 (affected, git); ≥ 20002ded4d937ca87aca6253b874920a96a763c4; < e9bbfb4bfa86c6b5515b868d6982ac60505d7e39 (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.32 (affected); ≥ 0; < 2.6.32 (unaffected, semver); ≥ 6.18.19; ≤ 6.18.* (unaffected, semver); ≥ 6.19.9; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.12% as of 2026-11-06; percentile 1.91%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/98074e16742ae87fb82e234b419783c5ffc9baea (CNA: Linux)

- https://git.kernel.org/stable/c/7e5f60b8cfc02a2b23a40a5f5fd2fa81d010e737 (CNA: Linux)

- https://git.kernel.org/stable/c/e9bbfb4bfa86c6b5515b868d6982ac60505d7e39 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-43416; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-43416; retrieved 2026-11-06; source updated Not reported

Revision: 7d5670469f9ac4842f7452188602f90282a6a2b4cc5d59bba73b6f7f99a94b2c

Canonical: https://y2.dev/cve/CVE-2026-43416

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