Add bpf_sysctl_get_name() helper to copy sysctl name (/proc/sys/ entry)
into provided by BPF_PROG_TYPE_CGROUP_SYSCTL program buffer.
By default full name (w/o /proc/sys/) is copied, e.g. "net/ipv4/tcp_mem".
If BPF_F_SYSCTL_BASE_NAME flag is set, only base name will be copied,
e.g. "tcp_mem".
Documentation for the new helper is provided in bpf.h UAPI.
Signed-off-by: Andrey Ignatov <rdna@xxxxxx>
---
include/uapi/linux/bpf.h | 22 ++++++++++++-
kernel/bpf/cgroup.c | 70 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 90 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4cfda9c16327..c9e8a1f22c14 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2479,6 +2479,22 @@ union bpf_attr {
* Return
* 0 if iph and th are a valid SYN cookie ACK, or a negative error
* otherwise.
+ *
+ * int bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf, size_t buf_len, u64 flags)
+ * Description
+ * Get name of sysctl in /proc/sys/ and copy it into provided by
+ * program buffer *buf* of size *buf_len*.
+ *
+ * The buffer is always NUL terminated, unless it's zero-sized.
+ *
+ * If *flags* is zero, full name (e.g. "net/ipv4/tcp_mem") is
+ * copied. Use **BPF_F_SYSCTL_BASE_NAME** flag to copy base name
+ * only (e.g. "tcp_mem").
+ * Return
+ * Number of character copied (not including the trailing NUL).
+ *
+ * **-E2BIG** if the buffer wasn't big enough (*buf* will contain
+ * truncated name in this case).
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2581,7 +2597,8 @@ union bpf_attr {
FN(skb_ecn_set_ce), \
FN(get_listener_sock), \
FN(skc_lookup_tcp), \
- FN(tcp_check_syncookie),
+ FN(tcp_check_syncookie), \
+ FN(sysctl_get_name),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -2648,6 +2665,9 @@ enum bpf_func_id {
#define BPF_F_ADJ_ROOM_ENCAP_L4_GRE (1ULL << 3)
#define BPF_F_ADJ_ROOM_ENCAP_L4_UDP (1ULL << 4)
+/* BPF_FUNC_sysctl_get_name flags. */
+#define BPF_F_SYSCTL_BASE_NAME (1ULL << 0)
+
/* Mode for BPF_FUNC_skb_adjust_room helper. */
enum bpf_adj_room_mode {
BPF_ADJ_ROOM_NET,
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 610491b5f0aa..a68387043244 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -14,6 +14,7 @@
#include <linux/filter.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
+#include <linux/string.h>
#include <linux/bpf.h>
#include <linux/bpf-cgroup.h>
#include <net/sock.h>
@@ -806,10 +807,77 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
}
EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl);
+static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp,
+ size_t *lenp)
+{
+ ssize_t tmp_ret = 0, ret;
+
+ if (dir->header.parent) {
+ tmp_ret = sysctl_cpy_dir(dir->header.parent, bufp, lenp);
+ if (tmp_ret < 0)
+ return tmp_ret;
+ }
+
+ ret = strscpy(*bufp, dir->header.ctl_table[0].procname, *lenp);
+ if (ret < 0)
+ return ret;
+ *bufp += ret;
+ *lenp -= ret;
+ ret += tmp_ret;
+
+ /* Avoid leading slash. */
+ if (!ret)
+ return ret;
+
+ tmp_ret = strscpy(*bufp, "/", *lenp);
+ if (tmp_ret < 0)
+ return tmp_ret;
+ *bufp += tmp_ret;
+ *lenp -= tmp_ret;
+
+ return ret + tmp_ret;
+}
+
+BPF_CALL_4(bpf_sysctl_get_name, struct bpf_sysctl_kern *, ctx, char *, buf,
+ size_t, buf_len, u64, flags)
+{
+ ssize_t tmp_ret = 0, ret;
+
+ if (!buf)
+ return -EINVAL;
+
+ if (!(flags & BPF_F_SYSCTL_BASE_NAME)) {
+ if (!ctx->head)
+ return -EINVAL;
+ tmp_ret = sysctl_cpy_dir(ctx->head->parent, &buf, &buf_len);
+ if (tmp_ret < 0)
+ return tmp_ret;
+ }
+
+ ret = strscpy(buf, ctx->table->procname, buf_len);
+
+ return ret < 0 ? ret : tmp_ret + ret;
+}
+
+static const struct bpf_func_proto bpf_sysctl_get_name_proto = {
+ .func = bpf_sysctl_get_name,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_PTR_TO_MEM,
+ .arg3_type = ARG_CONST_SIZE,
+ .arg4_type = ARG_ANYTHING,
+};
+
static const struct bpf_func_proto *
sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
- return cgroup_base_func_proto(func_id, prog);
+ switch (func_id) {
+ case BPF_FUNC_sysctl_get_name:
+ return &bpf_sysctl_get_name_proto;
+ default:
+ return cgroup_base_func_proto(func_id, prog);
+ }
}
static bool sysctl_is_valid_access(int off, int size, enum bpf_access_type type,
--
2.17.1
