| Message ID | 20191009152632.14218-3-cneirabustos@gmail.com |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | BPF: New helper to obtain namespace data from current task | expand |
On Wed, Oct 9, 2019 at 8:27 AM Carlos Neira <cneirabustos@gmail.com> 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@gmail.com> > --- > 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 <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 +489,44 @@ 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 >
On Wed, Oct 09, 2019 at 09:14:42AM -0700, Andrii Nakryiko wrote: > On Wed, Oct 9, 2019 at 8:27 AM Carlos Neira <cneirabustos@gmail.com> 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@gmail.com> > > --- > > 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 <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 +489,44 @@ 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 > > Thanks for reviewing this, I'll make the changes you suggest. I'm not sure about removing dev and ino from struct bpf_pidns_info, I think is useful to know to which ns pid/tgid belong to using dev and ino to figure it out. Maybe in the future we could filter bpf_pidns_info structs by dev/ino, just an idea. Bests
On Wed, Oct 9, 2019 at 10:45 AM Carlos Antonio Neira Bustos <cneirabustos@gmail.com> wrote: > > On Wed, Oct 09, 2019 at 09:14:42AM -0700, Andrii Nakryiko wrote: > > On Wed, Oct 9, 2019 at 8:27 AM Carlos Neira <cneirabustos@gmail.com> 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@gmail.com> > > > --- > > > 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 <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 +489,44 @@ 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 > > > > Thanks for reviewing this, I'll make the changes you suggest. > I'm not sure about removing dev and ino from struct bpf_pidns_info, I > think is useful to know to which ns pid/tgid belong to using dev and ino > to figure it out. Maybe in the future we could filter bpf_pidns_info > structs by dev/ino, just an idea. I'm not following. dev/ino are specified by the caller to this helper, right? So caller already know those values. With current set up, though, the behavior is weird: this struct's dev/ino is preserved on success, but zeroed out on failure, even though helper itself has nothing to do with returning dev/ino. It also plays badly with ARG_PTR_TO_UNINT_MEM, because that memory is expected to be at least partially initialized. I see only downsides, to be honest. > > Bests
On Wed, Oct 09, 2019 at 12:50:10PM -0700, Andrii Nakryiko wrote: > On Wed, Oct 9, 2019 at 10:45 AM Carlos Antonio Neira Bustos > <cneirabustos@gmail.com> wrote: > > > > On Wed, Oct 09, 2019 at 09:14:42AM -0700, Andrii Nakryiko wrote: > > > On Wed, Oct 9, 2019 at 8:27 AM Carlos Neira <cneirabustos@gmail.com> 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@gmail.com> > > > > --- > > > > 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 <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 +489,44 @@ 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 > > > > > > Thanks for reviewing this, I'll make the changes you suggest. > > I'm not sure about removing dev and ino from struct bpf_pidns_info, I > > think is useful to know to which ns pid/tgid belong to using dev and ino > > to figure it out. Maybe in the future we could filter bpf_pidns_info > > structs by dev/ino, just an idea. > > I'm not following. dev/ino are specified by the caller to this helper, > right? So caller already know those values. With current set up, > though, the behavior is weird: this struct's dev/ino is preserved on > success, but zeroed out on failure, even though helper itself has > nothing to do with returning dev/ino. It also plays badly with > ARG_PTR_TO_UNINT_MEM, because that memory is expected to be at least > partially initialized. I see only downsides, to be honest. > > > > > Bests Andrii, Oh you are right dev/ino are specific to the caller of this helper, and what you state is correct dev/ino are also not returned by the caller based on that, yes this should be changed. Now I see the point, I'll change the helper to take dev/ino and just return pid/tgid. Thanks again!. Bests
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) + * 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. + * + * 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; + __u32 pid; + __u32 tgid; +}; #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 <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 +489,44 @@ 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) + 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, + .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; }
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@gmail.com> --- 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(-)