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Message-ID: <c5ecd602-8b45-94bd-96e8-2264a88a3c09@fb.com>
Date: Tue, 10 Sep 2019 22:46:45 +0000
From: Yonghong Song <yhs@...com>
To: Carlos Neira <cneirabustos@...il.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC: "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
"brouer@...hat.com" <brouer@...hat.com>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v10 2/4] bpf: new helper to obtain namespace data
from current task New bpf helper bpf_get_current_pidns_info.
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@...il.com>
> ---
> 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;
> }
>
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