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authorJakub Kicinski <kuba@kernel.org>2022-09-29 17:28:09 +0300
committerJakub Kicinski <kuba@kernel.org>2022-10-01 03:43:09 +0300
commitcff2d762cde669023f345157f875b7ea6658992a (patch)
treee86e6a63dfb3a73cfd8ede815601e719044c51f8 /net/netlink/genetlink.c
parent915b96c52763e2988e6368b538b487a7138b8fa4 (diff)
downloadlinux-cff2d762cde669023f345157f875b7ea6658992a.tar.xz
genetlink: reject use of nlmsg_flags for new commands
Commit 9c5d03d36251 ("genetlink: start to validate reserved header bytes") introduced extra validation for genetlink headers. We had to gate it to only apply to new commands, to maintain bug-wards compatibility. Use this opportunity (before the new checks make it to Linus's tree) to add more conditions. Validate that Generic Netlink families do not use nlmsg_flags outside of the well-understood set. Link: https://lore.kernel.org/all/20220928073709.1b93b74a@kernel.org/ Reviewed-by: Johannes Berg <johannes@sipsolutions.net> Acked-by: Nikolay Aleksandrov <razor@blackwall.org> Reviewed-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Reviewed-by: Guillaume Nault <gnault@redhat.com> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Link: https://lore.kernel.org/r/20220929142809.1167546-1-kuba@kernel.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/netlink/genetlink.c')
-rw-r--r--net/netlink/genetlink.c32
1 files changed, 31 insertions, 1 deletions
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 7c136de117eb..39b7c00e4cef 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -739,6 +739,36 @@ out:
return err;
}
+static int genl_header_check(const struct genl_family *family,
+ struct nlmsghdr *nlh, struct genlmsghdr *hdr,
+ struct netlink_ext_ack *extack)
+{
+ u16 flags;
+
+ /* Only for commands added after we started validating */
+ if (hdr->cmd < family->resv_start_op)
+ return 0;
+
+ if (hdr->reserved) {
+ NL_SET_ERR_MSG(extack, "genlmsghdr.reserved field is not 0");
+ return -EINVAL;
+ }
+
+ /* Old netlink flags have pretty loose semantics, allow only the flags
+ * consumed by the core where we can enforce the meaning.
+ */
+ flags = nlh->nlmsg_flags;
+ if ((flags & NLM_F_DUMP) == NLM_F_DUMP) /* DUMP is 2 bits */
+ flags &= ~NLM_F_DUMP;
+ if (flags & ~(NLM_F_REQUEST | NLM_F_ACK | NLM_F_ECHO)) {
+ NL_SET_ERR_MSG(extack,
+ "ambiguous or reserved bits set in nlmsg_flags");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int genl_family_rcv_msg(const struct genl_family *family,
struct sk_buff *skb,
struct nlmsghdr *nlh,
@@ -757,7 +787,7 @@ static int genl_family_rcv_msg(const struct genl_family *family,
if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
return -EINVAL;
- if (hdr->cmd >= family->resv_start_op && hdr->reserved)
+ if (genl_header_check(family, nlh, hdr, extack))
return -EINVAL;
if (genl_get_cmd(hdr->cmd, family, &op))