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AJvYcCWOeUHcLEMqa7tYl09RhUgJVEKZ4ADuoUXmlL9KVKhudM3SzNB0S+oeKxXNSu2shwns4ZDPAUkWMBL7@vger.kernel.org X-Gm-Message-State: AOJu0Yy87NkGCaqS3sXC9BiIJPh+qQw6ird13K8muXTCw8RytAGaGdgg bSBQRiYltiQivWOAKKeJYlCBRaeAG222rgyY3KdkHZG1aQnQ63jyVkiNQSSEU7mfXBNXdwkCG24 oawbmnAher19IsnRKSG4vXiUfDOEtFU0QyKnS X-Google-Smtp-Source: AGHT+IFe+18jaYfQr+21B0WFTGQIwcQex+WsgK+bAeIFw8v1CVPL3tiWr1CxsaBhl5XE5hKvMkCXjZhdZbiCyhqn9EA= X-Received: by 2002:a05:6402:3495:b0:5c4:2e9f:4cfc with SMTP id 4fb4d7f45d1cf-5c95b38b9a3mr532129a12.6.1728936554221; Mon, 14 Oct 2024 13:09:14 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240903232241.43995-1-anthony.yznaga@oracle.com> <20240903232241.43995-6-anthony.yznaga@oracle.com> In-Reply-To: <20240903232241.43995-6-anthony.yznaga@oracle.com> From: Jann Horn Date: Mon, 14 Oct 2024 22:08:38 +0200 Message-ID: Subject: Re: [RFC PATCH v3 05/10] mm/mshare: Add ioctl support To: Anthony Yznaga Cc: akpm@linux-foundation.org, willy@infradead.org, markhemm@googlemail.com, viro@zeniv.linux.org.uk, david@redhat.com, khalid@kernel.org, andreyknvl@gmail.com, dave.hansen@intel.com, luto@kernel.org, brauner@kernel.org, arnd@arndb.de, ebiederm@xmission.com, catalin.marinas@arm.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhiramat@kernel.org, rostedt@goodmis.org, vasily.averin@linux.dev, xhao@linux.alibaba.com, pcc@google.com, neilb@suse.de, maz@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Sep 4, 2024 at 1:22=E2=80=AFAM Anthony Yznaga wrote: > Reserve a range of ioctls for msharefs and add the first two ioctls > to get and set the start address and size of an mshare region. [...] > +static long > +msharefs_set_size(struct mm_struct *mm, struct mshare_data *m_data, > + struct mshare_info *minfo) > +{ > + unsigned long end =3D minfo->start + minfo->size; > + > + /* > + * Validate alignment for start address, and size > + */ > + if ((minfo->start | end) & (PGDIR_SIZE - 1)) { > + spin_unlock(&m_data->m_lock); > + return -EINVAL; > + } > + > + mm->mmap_base =3D minfo->start; > + mm->task_size =3D minfo->size; > + if (!mm->task_size) > + mm->task_size--; > + > + m_data->minfo.start =3D mm->mmap_base; > + m_data->minfo.size =3D mm->task_size; > + spin_unlock(&m_data->m_lock); > + > + return 0; > +} > + > +static long > +msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > +{ > + struct mshare_data *m_data =3D filp->private_data; > + struct mm_struct *mm =3D m_data->mm; > + struct mshare_info minfo; > + > + switch (cmd) { > + case MSHAREFS_GET_SIZE: > + spin_lock(&m_data->m_lock); > + minfo =3D m_data->minfo; > + spin_unlock(&m_data->m_lock); > + > + if (copy_to_user((void __user *)arg, &minfo, sizeof(minfo= ))) > + return -EFAULT; > + > + return 0; > + > + case MSHAREFS_SET_SIZE: > + if (copy_from_user(&minfo, (struct mshare_info __user *)a= rg, > + sizeof(minfo))) > + return -EFAULT; > + > + /* > + * If this mshare region has been set up once already, ba= il out > + */ > + spin_lock(&m_data->m_lock); > + if (m_data->minfo.start !=3D 0) { Is there actually anything that prevents msharefs_set_size() from setting up m_data with ->minfo.start=3D=3D0, so that a second MSHAREFS_SET_SIZE invocation will succeed? It would probably be more reliable to have a separate flag for "has this thing been set up yet". > + spin_unlock(&m_data->m_lock); > + return -EINVAL; > + } > + > + return msharefs_set_size(mm, m_data, &minfo); > + > + default: > + return -ENOTTY; > + } > +}