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Message-ID: <CALCETrWzfgNvOHmKy5205A2qLJLYCZ+5RZOQR9vzQ1ubpo0vNA@mail.gmail.com> Date: Thu, 25 Aug 2016 04:12:02 -0700 From: Andy Lutomirski <luto@...capital.net> To: Mickaël Salaün <mic@...ikod.net>, "Eric W. Biederman" <ebiederm@...ssion.com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Arnd Bergmann <arnd@...db.de>, Casey Schaufler <casey@...aufler-ca.com>, Daniel Borkmann <daniel@...earbox.net>, Daniel Mack <daniel@...que.org>, David Drysdale <drysdale@...gle.com>, "David S . Miller" <davem@...emloft.net>, Elena Reshetova <elena.reshetova@...el.com>, James Morris <james.l.morris@...cle.com>, Kees Cook <keescook@...omium.org>, Paul Moore <pmoore@...hat.com>, Sargun Dhillon <sargun@...gun.me>, "Serge E . Hallyn" <serge@...lyn.com>, Will Drewry <wad@...omium.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Linux API <linux-api@...r.kernel.org>, LSM List <linux-security-module@...r.kernel.org>, Network Development <netdev@...r.kernel.org> Subject: Re: [RFC v2 08/10] landlock: Handle file system comparisons On Thu, Aug 25, 2016 at 3:32 AM, Mickaël Salaün <mic@...ikod.net> wrote: > Add eBPF functions to compare file system access with a Landlock file > system handle: > * bpf_landlock_cmp_fs_prop_with_struct_file(prop, map, map_op, file) > This function allows to compare the dentry, inode, device or mount > point of the currently accessed file, with a reference handle. > * bpf_landlock_cmp_fs_beneath_with_struct_file(opt, map, map_op, file) > This function allows an eBPF program to check if the current accessed > file is the same or in the hierarchy of a reference handle. > > The goal of file system handle is to abstract kernel objects such as a > struct file or a struct inode. Userland can create this kind of handle > thanks to the BPF_MAP_UPDATE_ELEM command. The element is a struct > landlock_handle containing the handle type (e.g. > BPF_MAP_HANDLE_TYPE_LANDLOCK_FS_FD) and a file descriptor. This could > also be any descriptions able to match a struct file or a struct inode > (e.g. path or glob string). This needs Eric's opinion. Also, where do all the struct file *'s get stashed? Are they preserved in the arraymap? What prevents reference cycles or absurdly large numbers of struct files getting pinned? --Andy
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