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bh=eMvRClh4q++3fIiRW757OjgsTI62ZCutkx+bitANNyk=; b=aXKCjm+YPVomM5NOCpMPdx+9Ou8iAv9tNIbEAIwdHJ3zNkopH+HWYIDPFxGMKS0/Ig y0FQeRbJvh4kWmwg9ghr0YvLT+CdNSNzViFMFVaooTBQKyfNcii1+TBsOLiQVCouRKi6 FsvPLrBzBZBCNbNtHtNVTD2Pq2ZMZIOTMCXIfNqZs3H0MUzRPgwrWB4mHyTUo8HqRve7 tIvUqBL/pB+o7qvlOcWS98xClFgVZ3tchfh30xS4VQLCe02+vmAxXlsnp4312k5u27ze sTJUGMs6UzyIAD2WqbRHPKCQQkILOr6Tg0MhLrUiqjAMILtY/68azaGAGt+9jLjLOkBB ickg== X-Gm-Message-State: APjAAAXfwZjNkudrIo0G4e1+XjCg0SvZzwfuRpI7LST/srONReLw8WAG VN+wRSS94xYhrl6AE2AvyByKt0Rdk62zH6UUJFFpFGG6+98= X-Google-Smtp-Source: APXvYqy33rDE+AJTOVTZfCxgPB7YAobojogyWf3KRqVCqFK7XRZ9AnJRo/gss1OWQvsEfxrJmYc12Nvfk5Kk8d2biDQ= X-Received: by 2002:ac8:5147:: with SMTP id h7mr4546118qtn.117.1570637695339; Wed, 09 Oct 2019 09:14:55 -0700 (PDT) MIME-Version: 1.0 References: <20191009152632.14218-1-cneirabustos@gmail.com> <20191009152632.14218-3-cneirabustos@gmail.com> In-Reply-To: <20191009152632.14218-3-cneirabustos@gmail.com> From: Andrii Nakryiko Date: Wed, 9 Oct 2019 09:14:42 -0700 Message-ID: Subject: Re: [PATCH v13 2/4] bpf: added new helper bpf_get_ns_current_pid_tgid To: Carlos Neira Cc: Networking , Yonghong Song , ebiederm@xmission.com, Jesper Dangaard Brouer , bpf Content-Type: text/plain; charset="UTF-8" Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Oct 9, 2019 at 8:27 AM 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 | 22 +++++++++++++++++++- > kernel/bpf/core.c | 1 + > kernel/bpf/helpers.c | 43 ++++++++++++++++++++++++++++++++++++++++ > kernel/trace/bpf_trace.c | 2 ++ > 5 files changed, 68 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..6ad3f2abf00d 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -2750,6 +2750,19 @@ 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(struct *bpf_pidns_info, u32 size) Should be: struct bpf_pidns_info *nsdata > + * Return > + * 0 on success, values for pid and tgid from nsinfo will be as seen > + * from the namespace that matches dev and inum from nsinfo. I think its cleaner to have a Description section, explaining that it will return pid/tgid in bpf_pidns_info, and then describe exit codes in Return section. > + * > + * 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 +2875,8 @@ 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 > @@ -3613,4 +3627,10 @@ struct bpf_sockopt { > __s32 retval; > }; > > +struct bpf_pidns_info { > + __u64 dev; > + __u64 inum; seems like conventionally this should be named "ino", this is what ns_match calls it, so let's stay consistent. > + __u32 pid; > + __u32 tgid; > +}; So it seems like dev and inum are treated as input parameters, while pid/tgid is output parameter, right? Wouldn't it be cleaner to have dev and inum as explicit arguments into bpf_get_ns_current_pid_tgid()? What's also not great, is that on failure you'll memset this entire struct to zero, and user will lose its dev/inum. So in practice you'll be keeping dev/inum somewhere else, then constructing and filling in this bpf_pidns_info struct every time you need to invoke bpf_get_ns_current_pid_tgid. Maybe it was discussed already, but IMO feels cleaner to have only pid/tgid in bpf_pidns_info and pass dev/inum as direct arguments. > #endif /* _UAPI__LINUX_BPF_H__ */ > 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..78a1ce7726aa 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 +489,44 @@ const struct bpf_func_proto bpf_strtoul_proto = { > .arg4_type = ARG_PTR_TO_LONG, > }; > #endif > + > +BPF_CALL_2(bpf_get_ns_current_pid_tgid, struct bpf_pidns_info *, nsdata, u32, > + size) > +{ > + struct task_struct *task = current; > + struct pid_namespace *pidns; > + int err = -EINVAL; > + > + if (unlikely(size != sizeof(struct bpf_pidns_info))) > + goto clear; > + > + if ((u64)(dev_t)nsdata->dev != nsdata->dev) this seems unlikely() as well :) > + goto clear; > + > + if (unlikely(!task)) > + goto clear; > + > + pidns = task_active_pid_ns(task); > + if (unlikely(!pidns)) { > + err = -ENOENT; > + goto clear; > + } > + > + if (!ns_match(&pidns->ns, (dev_t)nsdata->dev, nsdata->inum)) > + goto clear; > + > + nsdata->pid = task_pid_nr_ns(task, pidns); > + nsdata->tgid = task_tgid_nr_ns(task, pidns); > + return 0; > +clear: > + memset((void *)nsdata, 0, (size_t) size); > + return err; > +} > + > +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_PTR_TO_UNINIT_MEM, So this is a lie, you do expect part of that struct to be initialized. One more reason to just split off dev/inum(ino?). > + .arg2_type = ARG_CONST_SIZE, > +}; > 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; > } > -- > 2.20.1 >