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[85.250.93.211]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49264022e7dsm18736795e9.6.2026.06.24.13.31.52 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 24 Jun 2026 13:31:53 -0700 (PDT) From: sivany32@gmail.com To: linux-pm@vger.kernel.org Cc: rafael@kernel.org, daniel.lezcano@kernel.org, linux-kernel@vger.kernel.org, elazarl@gmail.com, Sivan Zohar-Kotzer Subject: [PATCH v2 1/2] powercap: dtpm_cpu: Guard em_cpu_get() against NULL return in sysfs callbacks Date: Wed, 24 Jun 2026 23:31:47 +0300 Message-Id: <20260624203147.67528-1-sivany32@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260611204658.47987-1-elazarl@gmail.com> References: <20260611204658.47987-1-elazarl@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sivan Zohar-Kotzer em_cpu_get() can return NULL when a CPU becomes impossible. Two call sites miss the NULL test: 1. set_pd_power_limit() — reachable from sysfs via the powercap constraint power_limit_uw store path. If the CPU has become impossible then pd will be NULL, return the current power limit unchanged (no-op) instead of crashing. 2. update_pd_power_uw() — called from CPU hotplug handlers via dtpm_update_power(). While reaching this with a NULL em may be technically impossible today, the check is kept for defense in depth against future refactoring or subtle races. The other sysfs-reachable path, get_pd_power_uw(), already has a NULL guard returning 0. Fixes: 0e8f68d7f048 ("powercap/drivers/dtpm: Add CPU energy model based support") Signed-off-by: Sivan Zohar-Kotzer Co-developed-by: Elazar Leibovich Signed-off-by: Elazar Leibovich --- 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 21355db64..886cbe922 100644 --- a/drivers/powercap/dtpm_cpu.c +++ b/drivers/powercap/dtpm_cpu.c @@ -47,6 +47,9 @@ static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit) u64 power; int i, nr_cpus; + if (!pd) + return dtpm->power_limit; + nr_cpus = cpumask_weight_and(cpu_online_mask, to_cpumask(pd->cpus)); rcu_read_lock(); @@ -125,6 +128,9 @@ static int update_pd_power_uw(struct dtpm *dtpm) struct em_perf_state *table; int nr_cpus; + if (!em) + return -EINVAL; + nr_cpus = cpumask_weight_and(cpu_online_mask, to_cpumask(em->cpus)); rcu_read_lock(); -- 2.39.5 (Apple Git-154)