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([2a05:6e02:1041:c10:21db:9254:19d9:645e]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4923fd15535sm399389615e9.3.2026.06.23.03.12.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jun 2026 03:12:32 -0700 (PDT) Message-ID: <60e8aeba-666c-453d-b2cb-3c45bb9723d2@oss.qualcomm.com> Date: Tue, 23 Jun 2026 12:12:32 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] powercap: dtpm_cpu: Guard em_cpu_get() against NULL return in sysfs callbacks To: Elazar Leibovich , linux-pm@vger.kernel.org Cc: "Rafael J . Wysocki" , Daniel Lezcano , linux-kernel@vger.kernel.org, Sivan Zohar-Kotzer References: <20260611204658.47987-1-elazarl@gmail.com> <20260611204658.47987-2-elazarl@gmail.com> Content-Language: en-US From: Daniel Lezcano In-Reply-To: <20260611204658.47987-2-elazarl@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: 2Jp6hMrTx7oHLz4efamHBqGle4jHqu1y X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIzMDA4MiBTYWx0ZWRfX2DuMDPk8+yDG 8321aQ4cEhQnO3hv32OOJSn7tQRlIJZg8sQa9SCob1eORvl67kywo7+CZWS2D+KglzqOVkcoipN Ks1SRkKH2eGrZ8CeT/OVNPslvbDXEMw= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIzMDA4MiBTYWx0ZWRfXxKZ8QvIFveAt 0BNnKU14EPAHpTtZaNNpIdDQ130P06Mcp+MyRMirJN2sNBx5Vgtdb0m+TG+GxaAFsSRRQGZuQs4 yhGQiKaeSBGXzpCKPrW0//jma+4/NpY3cmg5onYQfsS1dR+yf+kg0rZE0r5qYEaJrfCyjefVIY2 YSw8mYmlXZ3tiA4yKjyntHOrpfjKIocVylSOc71i1zDYFPMKv7MDJjbFJ2GNi3H/KsxAFlgIUF2 PLbugupKzTaQ+DgbOJHMfUd52fmyh/+BDedqZnf7MUOQmj4iqvd7Hf69n/osksBbi/ZKeJOPgk6 EXCZDPzu+vsfo0YsFIivmgR2aQtfhA3BRi8Hz/s9EDd21618f4KKSoHCjM3/L44wJtPpaTFOATp 9+0jphyAR/76z/Oc+edX7k6NKBOxqj2ZvPPi0hUzfjW3GRXZ0yhMCD1yoYTLUfPNKUGtTOm5rLA KNGvA1eIyBgG8EBkCZw== X-Proofpoint-GUID: 2Jp6hMrTx7oHLz4efamHBqGle4jHqu1y X-Authority-Analysis: v=2.4 cv=YpI/gYYX c=1 sm=1 tr=0 ts=6a3a5c12 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=ZpdpYltYx_vBUK5n70dp:22 a=pGLkceISAAAA:8 a=Xzsr67MKrT1HMcM2bGYA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-23_02,2026-06-22_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 clxscore=1015 spamscore=0 phishscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 suspectscore=0 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606230082 Hi, On 6/11/26 22:46, Elazar Leibovich wrote: > From: Sivan Zohar-Kotzer > > em_cpu_get() can return NULL when the CPU has no energy model registered > (e.g. during hotplug races or initialization failures). 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 NULL, return the current > power limit unchanged (no-op) instead of crashing. If there is no energy model, then __dtpm_cpu_setup() fails and dtpm_ops is not set. Consequently, set_pd_power_limit() can not be called. > 2. update_pd_power_uw() — called from CPU hotplug handlers via > dtpm_update_power(). Return -EINVAL if the EM is absent, since this > is an internal consistency failure that should not be swallowed. If there is no energy model, then __dtpm_cpu_setup() fails and dtpm_per_cpu is not set and dtpm_update_power() is not called. online/offline: if (dtpm_cpu) dtpm_update_power(&dtpm_cpu->dtpm); > 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 99390ec1481f..0a460f97bf15 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();