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Hermes SMTP Server) with ESMTPA ID af2e520e4fc25b996d153d4d132eb18f; Wed, 13 Nov 2024 18:29:59 +0000 (UTC) Message-ID: <1cd17944-8c1f-4b13-9ac5-912086fbead6@schaufler-ca.com> Date: Wed, 13 Nov 2024 10:29:57 -0800 Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next 2/4] bpf: Make bpf inode storage available to tracing program To: Song Liu , Christian Brauner Cc: Song Liu , "bpf@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-security-module@vger.kernel.org" , Kernel Team , "andrii@kernel.org" , "eddyz87@gmail.com" , "ast@kernel.org" , "daniel@iogearbox.net" , "martin.lau@linux.dev" , "viro@zeniv.linux.org.uk" , "jack@suse.cz" , "kpsingh@kernel.org" , "mattbobrowski@google.com" , "amir73il@gmail.com" , "repnop@google.com" , "jlayton@kernel.org" , Josef Bacik , "mic@digikod.net" , "gnoack@google.com" , Casey Schaufler References: <20241112082600.298035-1-song@kernel.org> <20241112082600.298035-3-song@kernel.org> <20241113-sensation-morgen-852f49484fd8@brauner> <2621E9B1-D3F7-47D5-A185-7EA47AF750B3@fb.com> Content-Language: en-US From: Casey Schaufler In-Reply-To: <2621E9B1-D3F7-47D5-A185-7EA47AF750B3@fb.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Mailer: WebService/1.1.22876 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo On 11/13/2024 6:15 AM, Song Liu wrote: > Hi Christian, > > Thanks for your review. > >> On Nov 13, 2024, at 2:19 AM, Christian Brauner wrote: > [...] > >>> diff --git a/include/linux/fs.h b/include/linux/fs.h >>> index 3559446279c1..479097e4dd5b 100644 >>> --- a/include/linux/fs.h >>> +++ b/include/linux/fs.h >>> @@ -79,6 +79,7 @@ struct fs_context; >>> struct fs_parameter_spec; >>> struct fileattr; >>> struct iomap_ops; >>> +struct bpf_local_storage; >>> >>> extern void __init inode_init(void); >>> extern void __init inode_init_early(void); >>> @@ -648,6 +649,9 @@ struct inode { >>> #ifdef CONFIG_SECURITY >>> void *i_security; >>> #endif >>> +#ifdef CONFIG_BPF_SYSCALL >>> + struct bpf_local_storage __rcu *i_bpf_storage; >>> +#endif >> Sorry, we're not growing struct inode for this. It just keeps getting >> bigger. Last cycle we freed up 8 bytes to shrink it and we're not going >> to waste them on special-purpose stuff. We already NAKed someone else's >> pet field here. > Would it be acceptable if we union i_bpf_storage with i_security? No! > IOW, if CONFIG_SECURITY is enabled, we will use existing logic. > If CONFIG_SECURITY is not enabled, we will use i_bpf_storage. > Given majority of default configs have CONFIG_SECURITY=y, this > will not grow inode for most users. OTOH, users with > CONFIG_SECURITY=n && CONFIG_BPF_SYSCALL=y combination can still > use inode local storage in the tracing BPF programs. > > Does this make sense? All it would take is one BPF programmer assuming that CONFIG_SECURITY=n is the norm for this to blow up spectacularly. > > Thanks, > Song >