2 files changed, 90 insertions, 2 deletions

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index cc2a2466d5f3..9c8a2f3ccb9b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2506,6 +2506,22 @@ 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),                     \
@@ -2608,7 +2624,8 @@ 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
@@ -2681,6 +2698,9 @@ enum bpf_func_id {
                                           BPF_ADJ_ROOM_ENCAP_L2_MASK) \
                                          << BPF_ADJ_ROOM_ENCAP_L2_SHIFT)
 
+/* 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,