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Date: Tue, 9 Aug 2016 17:00:12 -0700
From: Sargun Dhillon <sargun@...gun.me>
To: netdev@...r.kernel.org
Cc: alexei.starovoitov@...il.com, daniel@...earbox.net
Subject: [net-next v2 v2 1/2] bpf: Add bpf_current_task_in_cgroup helper
This adds a bpf helper that's similar to the skb_in_cgroup helper to check
whether the probe is currently executing in the context of a specific
subset of the cgroupsv2 hierarchy. It does this based on membership test
for a cgroup arraymap. It is invalid to call this in an interrupt, and
it'll return an error. The helper is primarily to be used in debugging
activities for containers, where you may have multiple programs running in
a given top-level "container".
This patch also genericizes some of the arraymap fetching logic between the
skb_in_cgroup helper and this new helper.
Signed-off-by: Sargun Dhillon <sargun@...gun.me>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
---
include/linux/bpf.h | 24 ++++++++++++++++++++++++
include/uapi/linux/bpf.h | 11 +++++++++++
kernel/bpf/arraymap.c | 2 +-
kernel/bpf/verifier.c | 4 +++-
kernel/trace/bpf_trace.c | 34 ++++++++++++++++++++++++++++++++++
net/core/filter.c | 11 ++++-------
6 files changed, 77 insertions(+), 9 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1113423..9adf712 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -319,4 +319,28 @@ extern const struct bpf_func_proto bpf_get_stackid_proto;
void bpf_user_rnd_init_once(void);
u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
+#ifdef CONFIG_CGROUPS
+/* Helper to fetch a cgroup pointer based on index.
+ * @map: a cgroup arraymap
+ * @idx: index of the item you want to fetch
+ *
+ * Returns pointer on success,
+ * Error code if item not found, or out-of-bounds access
+ */
+static inline struct cgroup *fetch_arraymap_ptr(struct bpf_map *map, int idx)
+{
+ struct cgroup *cgrp;
+ struct bpf_array *array = container_of(map, struct bpf_array, map);
+
+ if (unlikely(idx >= array->map.max_entries))
+ return ERR_PTR(-E2BIG);
+
+ cgrp = READ_ONCE(array->ptrs[idx]);
+ if (unlikely(!cgrp))
+ return ERR_PTR(-EAGAIN);
+
+ return cgrp;
+}
+#endif /* CONFIG_CGROUPS */
+
#endif /* _LINUX_BPF_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index da218fe..64b1a07 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -375,6 +375,17 @@ enum bpf_func_id {
*/
BPF_FUNC_probe_write_user,
+ /**
+ * bpf_current_task_in_cgroup(map, index) - Check cgroup2 membership of current task
+ * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
+ * @index: index of the cgroup in the bpf_map
+ * Return:
+ * == 0 current failed the cgroup2 descendant test
+ * == 1 current succeeded the cgroup2 descendant test
+ * < 0 error
+ */
+ BPF_FUNC_current_task_in_cgroup,
+
__BPF_FUNC_MAX_ID,
};
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 633a650..a2ac051 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -538,7 +538,7 @@ static int __init register_perf_event_array_map(void)
}
late_initcall(register_perf_event_array_map);
-#ifdef CONFIG_SOCK_CGROUP_DATA
+#ifdef CONFIG_CGROUPS
static void *cgroup_fd_array_get_ptr(struct bpf_map *map,
struct file *map_file /* not used */,
int fd)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7094c69..80efab8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1053,7 +1053,8 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
- if (func_id != BPF_FUNC_skb_in_cgroup)
+ if (func_id != BPF_FUNC_skb_in_cgroup &&
+ func_id != BPF_FUNC_current_task_in_cgroup)
goto error;
break;
default:
@@ -1075,6 +1076,7 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
+ case BPF_FUNC_current_task_in_cgroup:
case BPF_FUNC_skb_in_cgroup:
if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
goto error;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b20438f..39f0290 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -376,6 +376,36 @@ static const struct bpf_func_proto bpf_get_current_task_proto = {
.ret_type = RET_INTEGER,
};
+#ifdef CONFIG_CGROUPS
+static u64 bpf_current_task_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+ struct bpf_map *map = (struct bpf_map *)(long)r1;
+ struct css_set *cset;
+ struct cgroup *cgrp;
+ u32 idx = (u32)r2;
+
+ if (unlikely(in_interrupt()))
+ return -EINVAL;
+
+ cgrp = fetch_arraymap_ptr(map, idx);
+
+ if (unlikely(IS_ERR(cgrp)))
+ return PTR_ERR(cgrp);
+
+ cset = task_css_set(current);
+
+ return cgroup_is_descendant(cset->dfl_cgrp, cgrp);
+}
+
+static const struct bpf_func_proto bpf_current_task_in_cgroup_proto = {
+ .func = bpf_current_task_in_cgroup,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_CONST_MAP_PTR,
+ .arg2_type = ARG_ANYTHING,
+};
+#endif /* CONFIG_CGROUPS */
+
static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
@@ -407,6 +437,10 @@ static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
return &bpf_perf_event_read_proto;
case BPF_FUNC_probe_write_user:
return bpf_get_probe_write_proto();
+#ifdef CONFIG_CGROUPS
+ case BPF_FUNC_current_task_in_cgroup:
+ return &bpf_current_task_in_cgroup_proto;
+#endif
default:
return NULL;
}
diff --git a/net/core/filter.c b/net/core/filter.c
index b5add4e..7fda861 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2321,21 +2321,18 @@ static u64 bpf_skb_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *)(long)r1;
struct bpf_map *map = (struct bpf_map *)(long)r2;
- struct bpf_array *array = container_of(map, struct bpf_array, map);
struct cgroup *cgrp;
struct sock *sk;
- u32 i = (u32)r3;
+ u32 idx = (u32)r3;
sk = skb->sk;
if (!sk || !sk_fullsock(sk))
return -ENOENT;
- if (unlikely(i >= array->map.max_entries))
- return -E2BIG;
+ cgrp = fetch_arraymap_ptr(map, idx);
- cgrp = READ_ONCE(array->ptrs[i]);
- if (unlikely(!cgrp))
- return -EAGAIN;
+ if (unlikely(IS_ERR(cgrp)))
+ return PTR_ERR(cgrp);
return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);
}
--
2.7.4
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