On 9/6/19 4:09 PM, Carlos Neira wrote: > This helper(bpf_get_current_pidns_info) 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. > > Signed-off-by: Carlos Neira <cneirabustos@xxxxxxxxx> > --- > include/linux/bpf.h | 1 + > include/uapi/linux/bpf.h | 35 +++++++++++++++++++- > kernel/bpf/core.c | 1 + > kernel/bpf/helpers.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++ > kernel/trace/bpf_trace.c | 2 ++ > 5 files changed, 124 insertions(+), 1 deletion(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 5b9d22338606..819cb1c84be0 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_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 b5889257cc33..3ec9aa1438b7 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -2747,6 +2747,32 @@ union bpf_attr { > * **-EOPNOTSUPP** kernel configuration does not enable SYN cookies > * > * **-EPROTONOSUPPORT** IP packet version is not 4 or 6 > + * > + * int bpf_get_current_pidns_info(struct bpf_pidns_info *pidns, u32 size_of_pidns) > + * Description > + * Get tgid, pid and namespace id as seen by the current namespace, > + * and device major/minor numbers from /proc/self/ns/pid. Such > + * information is stored in *pidns* of size *size*. > + * > + * This helper is used when pid filtering is needed inside a > + * container as bpf_get_current_tgid() helper always returns the > + * pid id as seen by the root namespace. > + * Return > + * 0 on success > + * > + * On failure, the returned value is one of the following: > + * > + * **-EINVAL** if *size_of_pidns* is not valid or unable to get ns, pid > + * or tgid of the current task. > + * > + * **-ENOENT** if /proc/self/ns/pid does not exists. > + * > + * **-ENOENT** if /proc/self/ns does not exists. > + * > + * **-ENOMEM** if helper internal allocation fails. -ENOMEM can be removed. > + * > + * **-EPERM** if not able to call helper. > + * > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -2859,7 +2885,8 @@ union bpf_attr { > FN(sk_storage_get), \ > FN(sk_storage_delete), \ > FN(send_signal), \ > - FN(tcp_gen_syncookie), > + FN(tcp_gen_syncookie), \ > + FN(get_current_pidns_info), > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > * function eBPF program intends to call > @@ -3610,4 +3637,10 @@ struct bpf_sockopt { > __s32 retval; > }; > > +struct bpf_pidns_info { > + __u32 dev; /* dev_t from /proc/self/ns/pid inode */ /* dev_t of pid namespace pseudo file (typically /proc/seelf/ns/pid) after following symbolic link */ > + __u32 nsid; > + __u32 tgid; > + __u32 pid; > +}; > #endif /* _UAPI__LINUX_BPF_H__ */ > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index 8191a7db2777..3159f2a0188c 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -2038,6 +2038,7 @@ 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 5e28718928ca..8dbe6347893c 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -11,6 +11,11 @@ > #include <linux/uidgid.h> > #include <linux/filter.h> > #include <linux/ctype.h> > +#include <linux/pid_namespace.h> > +#include <linux/kdev_t.h> > +#include <linux/stat.h> > +#include <linux/namei.h> > +#include <linux/version.h> > > #include "../../lib/kstrtox.h" > > @@ -312,6 +317,87 @@ void copy_map_value_locked(struct bpf_map *map, void *dst, void *src, > preempt_enable(); > } > > +BPF_CALL_2(bpf_get_current_pidns_info, struct bpf_pidns_info *, pidns_info, u32, > + size) > +{ > + const char *pidns_path = "/proc/self/ns/pid"; > + struct pid_namespace *pidns = NULL; > + struct filename *fname = NULL; > + struct inode *inode; > + struct path kp; > + pid_t tgid = 0; > + pid_t pid = 0; > + int ret = -EINVAL; > + int len; > + > + if (unlikely(in_interrupt() || > + current->flags & (PF_KTHREAD | PF_EXITING))) > + return -EPERM; > + > + if (unlikely(size != sizeof(struct bpf_pidns_info))) > + return -EINVAL; > + > + pidns = task_active_pid_ns(current); > + if (unlikely(!pidns)) > + return -ENOENT; > + > + 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; > + [...] > + fname = kmem_cache_alloc(names_cachep, GFP_ATOMIC); > + if (unlikely(!fname)) { > + ret = -ENOMEM; > + goto clear; > + } > + const size_t fnamesize = offsetof(struct filename, iname[1]); > + struct filename *tmp; > + > + tmp = kmalloc(fnamesize, GFP_ATOMIC); > + if (unlikely(!tmp)) { > + __putname(fname); > + ret = -ENOMEM; > + goto clear; > + } > + > + tmp->name = (char *)fname; > + fname = tmp; > + len = strlen(pidns_path) + 1; > + memcpy((char *)fname->name, pidns_path, len); > + fname->uptr = NULL; > + fname->aname = NULL; > + fname->refcnt = 1; > + > + ret = filename_lookup(AT_FDCWD, fname, 0, &kp, NULL); > + if (ret) > + goto clear; > + > + inode = d_backing_inode(kp.dentry); > + pidns_info->dev = (u32)inode->i_rdev; The above can bee replaced with new nsfs interface function ns_get_inum_dev(). > + > + return 0; > + > +clear: > + memset((void *)pidns_info, 0, (size_t) size); > + return ret; > +} > + > +const struct bpf_func_proto bpf_get_current_pidns_info_proto = { > + .func = bpf_get_current_pidns_info, > + .gpl_only = false, > + .ret_type = RET_INTEGER, > + .arg1_type = ARG_PTR_TO_UNINIT_MEM, > + .arg2_type = ARG_CONST_SIZE, > +}; > + > #ifdef CONFIG_CGROUPS > BPF_CALL_0(bpf_get_current_cgroup_id) > { > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index ca1255d14576..5e1dc22765a5 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -709,6 +709,8 @@ 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_current_pidns_info: > + return &bpf_get_current_pidns_info_proto; > default: > return NULL; > } >