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Wed, 20 Mar 2019 18:23:22 -0700 (PDT) Date: Wed, 20 Mar 2019 18:23:20 -0700 From: Alexei Starovoitov To: Carlos Antonio Neira Bustos Cc: netdev@vger.kernel.org, ebiederm@xmission.com, quentin.monnet@netronome.com, ys114321@gmail.com, brouer@redhat.com Subject: Re: [PATCH v3 bpf-next 1/3] BPF: helpers: New helper to obtain namespace data from current task Message-ID: <20190321012318.yfaeo3fppxm4rtnv@ast-mbp.dhcp.thefacebook.com> References: <20190320164920.ha5ne7nlnu7fbx5i@dev00> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320164920.ha5ne7nlnu7fbx5i@dev00> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Mar 20, 2019 at 01:49:22PM -0300, Carlos Antonio Neira Bustos wrote: > > This is a series of patches to introduce a new helper called bpf_get_current_pidns_info, > this change has been splitted into the following patches: > > 1- Feature introduction > 2- Update tools/.../bpf.h > 3- Self tests and samples > > > From 852a65906122b05b4d1a23af868b2c245d240402 Mon Sep 17 00:00:00 2001 > From: Carlos > Date: Tue, 19 Mar 2019 19:38:48 -0300 > Subject: [PATCH] [PATCH bpf-next 1/3] BPF: New helper to obtain namespace data > from current task > > This helper obtains the active namespace from current and returns pid, tgid, > device and namespace id as seen from that namespace, allowing to instrument > a process inside a container. > Device is read from /proc/self/ns/pid, as in the future it's possible that > different pid_ns files may belong to different devices, according > to the discussion between Eric Biederman and Yonghong in 2017 linux plumbers > conference. > Currently bpf_get_current_pid_tgid(), is used to do pid filtering in bcc's > scripts but this helper returns the pid as seen by the root namespace which is > fine when a bcc script is not executed inside a container. > When the process of interest is inside a container, pid filtering will not work > if bpf_get_current_pid_tgid() is used. This helper addresses this limitation > returning the pid as it's seen by the current namespace where the script is > executing. > > This helper has the same use cases as bpf_get_current_pid_tgid() as it can be > used to do pid filtering even inside a container. > > For example a bcc script using bpf_get_current_pid_tgid() (tools/funccount.py): > > u32 pid = bpf_get_current_pid_tgid() >> 32; > if (pid != ) > return 0; > Could be modified to use bpf_get_current_pidns_info() as follows: > > struct bpf_pidns pidns; > bpf_get_current_pidns_info(&pidns, sizeof(struct bpf_pidns)); > u32 pid = pidns.tgid; > u32 nsid = pidns.nsid; > if ((pid != ) && (nsid != )) > return 0; > > To find out the name PID namespace id of a process, you could use this command: > > $ ps -h -o pidns -p > > Or this other command: > > $ ls -Li /proc//ns/pid > > Signed-off-by: Carlos Antonio Neira Bustos > - > --- > include/linux/bpf.h | 1 + > include/uapi/linux/bpf.h | 26 ++++++++++++++++++- > kernel/bpf/core.c | 1 + > kernel/bpf/helpers.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++ > kernel/trace/bpf_trace.c | 2 ++ > 5 files changed, 96 insertions(+), 1 deletion(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index a2132e09dc1c..a77f5bd77bd8 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -930,6 +930,7 @@ extern const struct bpf_func_proto bpf_sk_redirect_map_proto; > extern const struct bpf_func_proto bpf_spin_lock_proto; > extern const struct bpf_func_proto bpf_spin_unlock_proto; > extern const struct bpf_func_proto bpf_get_local_storage_proto; > +extern const struct bpf_func_proto bpf_get_current_pidns_info_proto; > > /* Shared helpers among cBPF and eBPF. */ > void bpf_user_rnd_init_once(void); > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 3c38ac9a92a7..facc701c7873 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -2366,6 +2366,18 @@ union bpf_attr { > * current value is ect (ECN capable). Works with IPv6 and IPv4. > * Return > * 1 if set, 0 if not set. > + * > + * int bpf_get_current_pidns_info(struct bpf_pidns_info *pidns, u32 size_of_pidns) > + * Description > + * Copies into *pidns* pid, namespace id and tgid as seen by the > + * current namespace and also device from /proc/self/ns/pid. > + * *size_of_pidns* must be the size of *pidns* > + * > + * This helper is used when pid filtering is needed inside a > + * container as bpf_get_current_tgid() helper returns always the > + * pid id as seen by the root namespace. > + * Return > + * 0 on success -EINVAL on error. > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -2465,7 +2477,8 @@ union bpf_attr { > FN(spin_unlock), \ > FN(sk_fullsock), \ > FN(tcp_sock), \ > - FN(skb_ecn_set_ce), > + FN(skb_ecn_set_ce), \ > + FN(get_current_pidns_info), > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > * function eBPF program intends to call > @@ -3152,4 +3165,15 @@ struct bpf_line_info { > struct bpf_spin_lock { > __u32 val; > }; > + > +/* helper bpf_get_current_pidns_info will store the following > + * data, dev will contain major/minor from /proc/self/pid. > +*/ > +struct bpf_pidns_info { > + __u32 dev; > + __u32 nsid; > + __u32 tgid; > + __u32 pid; > +}; > + > #endif /* _UAPI__LINUX_BPF_H__ */ > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index 3f08c257858e..06329fbed95f 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -2044,6 +2044,7 @@ const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak; > const struct bpf_func_proto bpf_get_current_comm_proto __weak; > const struct bpf_func_proto bpf_get_current_cgroup_id_proto __weak; > const struct bpf_func_proto bpf_get_local_storage_proto __weak; > +const struct bpf_func_proto bpf_get_current_pidns_info __weak; > > const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void) > { > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index a411fc17d265..95c3780a6ba7 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -18,6 +18,11 @@ > #include > #include > #include > +#include > +#include > +#include > +#include > +#include > > /* If kernel subsystem is allowing eBPF programs to call this function, > * inside its own verifier_ops->get_func_proto() callback it should return > @@ -364,3 +369,65 @@ const struct bpf_func_proto bpf_get_local_storage_proto = { > }; > #endif > #endif > + > +BPF_CALL_2(bpf_get_current_pidns_info, struct bpf_pidns_info *, pidns_info, u32, > + size) > +{ > + const char *nspid = "/proc/self/ns/pid"; > + struct pid_namespace *pidns = NULL; > + struct kstat ks; > + struct path kp; > + pid_t tgid = 0; > + pid_t pid = 0; > + int res = 0; > + > + if (unlikely(size != sizeof(struct bpf_pidns_info))) > + goto clear; > + > + pidns = task_active_pid_ns(current); > + > + if (unlikely(!pidns)) > + goto clear; > + > + pidns_info->nsid = pidns->ns.inum; > + pid = task_pid_nr_ns(current, pidns); > + > + if (unlikely(!pid)) > + goto clear; > + > + tgid = task_tgid_nr_ns(current, pidns); > + > + if (unlikely(!tgid)) > + goto clear; > + > + pidns_info->tgid = (u32) tgid; > + pidns_info->pid = (u32) pid; > + > + kern_path(nspid, 0, &kp); > + > +#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0) > + res = vfs_getattr(&kp, &ks, STATX_ALL, 0); > +#else > + res = vfs_getattr(&kp, &ks); > +#endif Please access namespaces directly. I suspect bpf helpers cannot do vfs_getattr. Something inside might sleep while bpf progs are non preemptible. Also please run ./scripts/checkpatch.pl on your patches and read Documentation/bpf/bpf_devel_QA.rst.