From bdcc85c2b05a9378d8bd2d65f9fc41440a3cf464 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Mon, 15 Jun 2026 14:31:25 -0400 Subject: [PATCH] nfsd: validate sockaddr length per family in listener_set nfsd_sock_nl_policy declares NFSD_A_SOCK_ADDR as a bare NLA_BINARY attribute with no minimum length. A CAP_NET_ADMIN caller can send a 16-byte NFSD_A_SOCK_ADDR with sa_family=AF_INET6, causing a 12-byte OOB read across three consumers (rpc_cmp_addr_port, svc_find_listener, kernel_bind). nfsd_nl_listener_set_doit() also parsed and validated each listener entry inline in two separate loops, interleaved with mutating the running listener configuration. The validation was duplicated, used an open-coded "nla_len < sizeof(struct sockaddr)" check that was too short for AF_INET6, and handled a malformed entry inconsistently depending on which loop noticed it. Add an nfsd_nl_validate_listeners() helper that walks the entire list once and confirms each entry parses, carries both an address and a transport name, and is long enough for its address family (sizeof(struct sockaddr_in) for AF_INET, sizeof(struct sockaddr_in6) for AF_INET6, -EAFNOSUPPORT otherwise). Call it before taking nfsd_mutex or creating the serv, so a malformed request fails cleanly with no side effects. Since every entry is known valid by the time the two existing loops run, drop the redundant presence and per-family length checks from both, leaving only the nla_parse_nested() call needed to extract the data. Fixes: 16a471177496 ("NFSD: add listener-{set,get} netlink command") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260615-nfsd-testing-v5-1-188d75aedda0@kernel.org Signed-off-by: Chuck Lever --- fs/nfsd/nfsctl.c | 77 ++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 65 insertions(+), 12 deletions(-) diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index f1ecbb13f642..caf59421f8f4 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1971,6 +1971,60 @@ int nfsd_nl_version_get_doit(struct sk_buff *skb, struct genl_info *info) return err; } +/** + * nfsd_nl_validate_listeners - sanity-check the listener list from userland + * @info: netlink metadata and command arguments + * + * Walk every NFSD_A_SERVER_SOCK_ADDR attribute and confirm that each entry + * is well-formed: it parses against the policy, carries both an address and + * a transport name, and the address is long enough for its family. Doing + * this up front lets the callers below assume every entry is valid and + * guarantees we make no changes when the request is malformed. + * + * Return: 0 if every entry is valid, or a negative errno otherwise. + */ +static int nfsd_nl_validate_listeners(struct genl_info *info) +{ + const struct nlattr *attr; + int rem; + + nlmsg_for_each_attr_type(attr, NFSD_A_SERVER_SOCK_ADDR, info->nlhdr, + GENL_HDRLEN, rem) { + struct nlattr *tb[NFSD_A_SOCK_MAX + 1]; + struct sockaddr *sa; + int err; + + err = nla_parse_nested(tb, NFSD_A_SOCK_MAX, attr, + nfsd_sock_nl_policy, info->extack); + if (err < 0) + return err; + + if (!tb[NFSD_A_SOCK_ADDR] || !tb[NFSD_A_SOCK_TRANSPORT_NAME]) + return -EINVAL; + + sa = nla_data(tb[NFSD_A_SOCK_ADDR]); + if (nla_len(tb[NFSD_A_SOCK_ADDR]) < sizeof(sa->sa_family)) + return -EINVAL; + + switch (sa->sa_family) { + case AF_INET: + if (nla_len(tb[NFSD_A_SOCK_ADDR]) < + sizeof(struct sockaddr_in)) + return -EINVAL; + break; + case AF_INET6: + if (nla_len(tb[NFSD_A_SOCK_ADDR]) < + sizeof(struct sockaddr_in6)) + return -EINVAL; + break; + default: + return -EAFNOSUPPORT; + } + } + + return 0; +} + /** * nfsd_nl_listener_set_doit - set the nfs running sockets * @skb: reply buffer @@ -1989,6 +2043,15 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info) bool delete = false; int err, rem; + /* + * Validate the entire listener list before making any changes, so a + * malformed request fails cleanly without creating a serv or touching + * the existing listeners. + */ + err = nfsd_nl_validate_listeners(info); + if (err) + return err; + mutex_lock(&nfsd_mutex); err = nfsd_create_serv(net); @@ -2015,16 +2078,11 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info) const char *xcl_name; struct sockaddr *sa; + /* validated up front in nfsd_nl_validate_listeners() */ if (nla_parse_nested(tb, NFSD_A_SOCK_MAX, attr, nfsd_sock_nl_policy, info->extack) < 0) continue; - if (!tb[NFSD_A_SOCK_ADDR] || !tb[NFSD_A_SOCK_TRANSPORT_NAME]) - continue; - - if (nla_len(tb[NFSD_A_SOCK_ADDR]) < sizeof(*sa)) - continue; - xcl_name = nla_data(tb[NFSD_A_SOCK_TRANSPORT_NAME]); sa = nla_data(tb[NFSD_A_SOCK_ADDR]); @@ -2076,16 +2134,11 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info) struct sockaddr *sa; int ret; + /* validated up front in nfsd_nl_validate_listeners() */ if (nla_parse_nested(tb, NFSD_A_SOCK_MAX, attr, nfsd_sock_nl_policy, info->extack) < 0) continue; - if (!tb[NFSD_A_SOCK_ADDR] || !tb[NFSD_A_SOCK_TRANSPORT_NAME]) - continue; - - if (nla_len(tb[NFSD_A_SOCK_ADDR]) < sizeof(*sa)) - continue; - xcl_name = nla_data(tb[NFSD_A_SOCK_TRANSPORT_NAME]); sa = nla_data(tb[NFSD_A_SOCK_ADDR]);