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(109-186-135-251.bb.netvision.net.il. [109.186.135.251]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4535e9a7ee3sm9987035e9.39.2025.06.18.16.16.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Jun 2025 16:16:46 -0700 (PDT) From: Sivan Zohar-Kotzer To: Daniel Lezcano , "Rafael J . Wysocki" Cc: elazarl@gmail.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Sivan Zohar-Kotzer Subject: [PATCH] powercap: dtpm_cpu: Fix NULL pointer dereference race during CPU offlining Date: Thu, 19 Jun 2025 02:16:31 +0300 Message-ID: <20250618231632.113471-1-sivany32@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The get_pd_power_uw() function contains a race condition during CPU offlining: * DTPM power calculations are triggered (e.g., via sysfs reads) while CPU i= s online * The CPU goes offline during the calculation, before em_cpu_get() is called * em_cpu_get() now returns NULL since the energy model was unregistered * em_span_cpus() dereferences the NULL pointer, causing a crash Commit eb82bace8931 introduced the call to em_span_cpus(pd) without checking if pd is NULL. Add a NULL check after em_cpu_get() and return 0 power if no energy model is available, matching the existing fallback behavior. Fixes: eb82bace8931 ("powercap/drivers/dtpm: Scale the power with the load") Signed-off-by: Sivan Zohar-Kotzer --- drivers/powercap/dtpm_cpu.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c index 6b6f51b21550..80d93ab4dc54 100644 --- a/drivers/powercap/dtpm_cpu.c +++ b/drivers/powercap/dtpm_cpu.c @@ -97,6 +97,11 @@ static u64 get_pd_power_uw(struct dtpm *dtpm) =20 pd =3D em_cpu_get(dtpm_cpu->cpu); =20 + if (!pd) { + pr_warn("DTPM: No energy model available for CPU%d\n", dtpm_cpu->cpu); + return 0; + } + pd_mask =3D em_span_cpus(pd); =20 freq =3D cpufreq_quick_get(dtpm_cpu->cpu); @@ -207,6 +212,7 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *paren= t) pd =3D em_cpu_get(cpu); if (!pd || em_is_artificial(pd)) { ret =3D -EINVAL; + goto release_policy; } =20 --=20 2.45.2