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.
+ *
+ * **-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 */
+ __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;
+
+ 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;
}
--
2.11.0
