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[35.197.141.202]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-715e575c4a0sm1666991b3a.201.2024.08.29.17.06.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2024 17:06:58 -0700 (PDT) Date: Fri, 30 Aug 2024 00:06:51 +0000 From: Pranjal Shrivastava To: Nicolin Chen Cc: Joerg Roedel , Will Deacon , Robin Murphy , Mostafa Saleh , "iommu@lists.linux.dev" Subject: Re: [PATCH v2 2/2] iommu/arm-smmu-v3: Adopt arm_smmu_event in handlers Message-ID: References: <20240827193026.3993039-1-praan@google.com> <20240827193026.3993039-3-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Aug 28, 2024 at 10:20:02PM -0700, Nicolin Chen wrote: > Hi Pranjal, > > On Tue, Aug 27, 2024 at 12:30:26PM -0700, Pranjal Shrivastava wrote: > > > /* Stage-2 is always pinned at the moment */ > > - if (evt[1] & EVTQ_1_S2) > > + if (event->stage) > > return -EFAULT; > > Should it be named to "s2" v.s stage? Sure, will rename it with the next version. > > > - mutex_lock(&smmu->streams_mutex); > > - master = arm_smmu_find_master(smmu, sid); > > - if (!master) { > > - ret = -EINVAL; > > - goto out_unlock; > > - } > > + if (!event->master) > > + return -EINVAL; > > > > - ret = iommu_report_device_fault(master->dev, &fault_evt); > > -out_unlock: > > - mutex_unlock(&smmu->streams_mutex); > > + ret = iommu_report_device_fault(event->master->dev, &fault_evt); > > The iommu_report_device_fault(master->dev) call lost its mutex > lock. I wonder if it could be unsafe to continue with that dev > pointer. Ack, I agree, responded with [Patch 1/2] in detail. In summary, we need to avoid the following situation: 1. The evtq_thread gets scheduled 2. arm_smmu_release_device removes the `master` & its streams 3. In the `handle_evt` we dereference `master` which has been `kfree`ed (also, we don't return -EINVAL in that case as we ideally should) I'll add back the `arm_smmu_find_master` in the the `arm_smmu_handle_evt` along with the locks. Nice catch! :) > > Nicolin Thanks, Pranjal