| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20191003181218.GA12598@frodo.byteswizards.com>
Date: Thu, 3 Oct 2019 15:12:18 -0300
From: Carlos Antonio Neira Bustos <cneirabustos@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Networking <netdev@...r.kernel.org>, Yonghong Song <yhs@...com>,
ebiederm@...ssion.com, Jesper Dangaard Brouer <brouer@...hat.com>,
bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH V12 2/4] bpf: added new helper bpf_get_ns_current_pid_tgid
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
> <cneirabustos@...il.com> 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 <cneirabustos@...il.com>
> > > > ---
> > > > 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 <linux/uidgid.h>
> > > > #include <linux/filter.h>
> > > > #include <linux/ctype.h>
> > > > +#include <linux/pid_namespace.h>
> > > > +#include <linux/proc_ns.h>
> > > > #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.
Powered by blists - more mailing lists