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Thu, 03 Oct 2019 11:12:23 -0700 (PDT) Date: Thu, 3 Oct 2019 15:12:18 -0300 From: Carlos Antonio Neira Bustos To: Andrii Nakryiko Cc: Daniel Borkmann , Networking , Yonghong Song , ebiederm@xmission.com, Jesper Dangaard Brouer , bpf Subject: Re: [PATCH V12 2/4] bpf: added new helper bpf_get_ns_current_pid_tgid Message-ID: <20191003181218.GA12598@frodo.byteswizards.com> References: <20191001214141.6294-1-cneirabustos@gmail.com> <20191001214141.6294-3-cneirabustos@gmail.com> <79645731-da32-6071-e05f-6345cf47bcd1@iogearbox.net> <20191003145211.GA3657@frodo.byteswizards.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Oct 03, 2019 at 10:30:06AM -0700, Andrii Nakryiko wrote: > On Thu, Oct 3, 2019 at 8:01 AM Carlos Antonio Neira Bustos > wrote: > > > > On Wed, Oct 02, 2019 at 12:52:29PM +0200, Daniel Borkmann wrote: > > > On 10/1/19 11:41 PM, Carlos Neira wrote: > > > > New bpf helper bpf_get_ns_current_pid_tgid, > > > > This helper will return pid and tgid from current task > > > > which namespace matches dev_t and inode number provided, > > > > this will allows us to instrument a process inside a container. > > > > > > > > Signed-off-by: Carlos Neira > > > > --- > > > > include/linux/bpf.h | 1 + > > > > include/uapi/linux/bpf.h | 18 +++++++++++++++++- > > > > kernel/bpf/core.c | 1 + > > > > kernel/bpf/helpers.c | 36 ++++++++++++++++++++++++++++++++++++ > > > > kernel/trace/bpf_trace.c | 2 ++ > > > > 5 files changed, 57 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > > > index 5b9d22338606..231001475504 100644 > > > > --- a/include/linux/bpf.h > > > > +++ b/include/linux/bpf.h > > > > @@ -1055,6 +1055,7 @@ extern const struct bpf_func_proto bpf_get_local_storage_proto; > > > > extern const struct bpf_func_proto bpf_strtol_proto; > > > > extern const struct bpf_func_proto bpf_strtoul_proto; > > > > extern const struct bpf_func_proto bpf_tcp_sock_proto; > > > > +extern const struct bpf_func_proto bpf_get_ns_current_pid_tgid_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 77c6be96d676..ea8145d7f897 100644 > > > > --- a/include/uapi/linux/bpf.h > > > > +++ b/include/uapi/linux/bpf.h > > > > @@ -2750,6 +2750,21 @@ union bpf_attr { > > > > * **-EOPNOTSUPP** kernel configuration does not enable SYN cookies > > > > * > > > > * **-EPROTONOSUPPORT** IP packet version is not 4 or 6 > > > > + * > > > > + * u64 bpf_get_ns_current_pid_tgid(u64 dev, u64 inum) > > > > + * Return > > > > + * A 64-bit integer containing the current tgid and pid from current task > > > > + * which namespace inode and dev_t matches , and is create as such: > > > > + * *current_task*\ **->tgid << 32 \|** > > > > + * *current_task*\ **->pid**. > > > > + * > > > > + * On failure, the returned value is one of the following: > > > > + * > > > > + * **-EINVAL** if dev and inum supplied don't match dev_t and inode number > > > > + * with nsfs of current task, or if dev conversion to dev_t lost high bits. > > > > + * > > > > + * **-ENOENT** if /proc/self/ns does not exists. > > > > + * > > > > */ > > > > #define __BPF_FUNC_MAPPER(FN) \ > > > > FN(unspec), \ > > > > @@ -2862,7 +2877,8 @@ union bpf_attr { > > > > FN(sk_storage_get), \ > > > > FN(sk_storage_delete), \ > > > > FN(send_signal), \ > > > > - FN(tcp_gen_syncookie), > > > > + FN(tcp_gen_syncookie), \ > > > > + FN(get_ns_current_pid_tgid), > > > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > > > > * function eBPF program intends to call > > > > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > > > > index 66088a9e9b9e..b2fd5358f472 100644 > > > > --- a/kernel/bpf/core.c > > > > +++ b/kernel/bpf/core.c > > > > @@ -2042,6 +2042,7 @@ 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_ns_current_pid_tgid_proto __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 5e28718928ca..8777181d1717 100644 > > > > --- a/kernel/bpf/helpers.c > > > > +++ b/kernel/bpf/helpers.c > > > > @@ -11,6 +11,8 @@ > > > > #include > > > > #include > > > > #include > > > > +#include > > > > +#include > > > > #include "../../lib/kstrtox.h" > > > > @@ -487,3 +489,37 @@ const struct bpf_func_proto bpf_strtoul_proto = { > > > > .arg4_type = ARG_PTR_TO_LONG, > > > > }; > > > > #endif > > > > + > > > > +BPF_CALL_2(bpf_get_ns_current_pid_tgid, u64, dev, u64, inum) > > > > +{ > > > > + struct task_struct *task = current; > > > > + struct pid_namespace *pidns; > > > > + pid_t pid, tgid; > > > > + > > > > + if ((u64)(dev_t)dev != dev) > > > > + return -EINVAL; > > > > + > > > > + if (unlikely(!task)) > > > > + return -EINVAL; > > > > + > > > > + pidns = task_active_pid_ns(task); > > > > + if (unlikely(!pidns)) > > > > + return -ENOENT; > > > > + > > > > + > > > > + if (!ns_match(&pidns->ns, (dev_t)dev, inum)) > > > > + return -EINVAL; > > > > + > > > > + pid = task_pid_nr_ns(task, pidns); > > > > + tgid = task_tgid_nr_ns(task, pidns); > > > > + > > > > + return (u64) tgid << 32 | pid; > > > > > > Basically here you are overlapping the 64-bit return value for the valid > > > outcome with the error codes above for the invalid case. If you look at > > > bpf_perf_event_read() we already had such broken occasion that bit us in > > > the past, and needed to introduce bpf_perf_event_read_value() instead. > > > Lets not go there again and design it similarly to the latter. > > > > > > > +} > > > > + > > > > +const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto = { > > > > + .func = bpf_get_ns_current_pid_tgid, > > > > + .gpl_only = false, > > > > + .ret_type = RET_INTEGER, > > > > + .arg1_type = ARG_ANYTHING, > > > > + .arg2_type = ARG_ANYTHING, > > > > +}; > > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > > > index 44bd08f2443b..32331a1dcb6d 100644 > > > > --- a/kernel/trace/bpf_trace.c > > > > +++ b/kernel/trace/bpf_trace.c > > > > @@ -735,6 +735,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > > > #endif > > > > case BPF_FUNC_send_signal: > > > > return &bpf_send_signal_proto; > > > > + case BPF_FUNC_get_ns_current_pid_tgid: > > > > + return &bpf_get_ns_current_pid_tgid_proto; > > > > default: > > > > return NULL; > > > > } > > > > > > > > > Daniel, > > If I understand correctly, to avoid problems I need to change the helper's function signature to something like the following: > > > > struct bpf_ns_current_pid_tgid_storage { > > __u64 dev; > > __u64 inum; > > __u64 pidtgid; > > if you do it this way, please do > > __u32 pid; > __u34 tgid; > > I have to look up where pid and tgid is in that 64-bit number every > single time, let's not do it here for no good reason. > > > }; > > > > BPF_CALL_2(bpf_get_ns_current_pid_tgid, > > struct bpf_ns_current_pid_tgid_storage *, buf, u32, size); > > > > then use dev and inum provided by the user and return the requested > > value into pidtgid of the struct. Would that work? > > > > Thanks for your help. > > > > > > > > Andrii, You are right, I'll do so. Bests.