bpf: Add length check for SK_DIAG_BPF_STORAGE_REQ_MAP_FD parsing

The nla_for_each_nested parsing in function bpf_sk_storage_diag_alloc
does not check the length of the nested attribute. This can lead to an
out-of-attribute read and allow a malformed nlattr (e.g., length 0) to
be viewed as a 4 byte integer.

This patch adds an additional check when the nlattr is getting counted.
This makes sure the latter nla_get_u32 can access the attributes with
the correct length.

Fixes: 1ed4d92458a9 ("bpf: INET_DIAG support in bpf_sk_storage")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230725023330.422856-1-linma@zju.edu.cn
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index d417253..cca7594 100644 (file)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -496,8 +496,11 @@ bpf_sk_storage_diag_alloc(const struct nlattr *nla_stgs)
                return ERR_PTR(-EPERM);
 
        nla_for_each_nested(nla, nla_stgs, rem) {
-               if (nla_type(nla) == SK_DIAG_BPF_STORAGE_REQ_MAP_FD)
+               if (nla_type(nla) == SK_DIAG_BPF_STORAGE_REQ_MAP_FD) {
+                       if (nla_len(nla) != sizeof(u32))
+                               return ERR_PTR(-EINVAL);
                        nr_maps++;
+               }
        }
 
        diag = kzalloc(struct_size(diag, maps, nr_maps), GFP_KERNEL);