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Message-ID: <20240305185000.964773-1-kuba@kernel.org>
Date: Tue, 5 Mar 2024 10:50:00 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
nicolas.dichtel@...nd.com,
jiri@...nulli.us,
donald.hunter@...il.com,
Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next] tools: ynl: check for overflow of constructed messages
Donald points out that we don't check for overflows.
Stash the length of the message on nlmsg_pid (nlmsg_seq would
do as well). This allows the attribute helpers to remain
self-contained (no extra arguments). Also let the put
helpers continue to return nothing. The error is checked
only in (newly introduced) ynl_msg_end().
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
This was first discussed when I posted the libmnl replacement:
https://lore.kernel.org/all/CAD4GDZzF55bkoZ_o0S784PmfW4+L_QrG2ofWg6CeQk4FCWTUiw@mail.gmail.com/
---
tools/net/ynl/lib/ynl-priv.h | 34 ++++++++++++++++++++++++++++++----
tools/net/ynl/lib/ynl.c | 36 ++++++++++++++++++++++++++++++++++++
tools/net/ynl/lib/ynl.h | 2 ++
3 files changed, 68 insertions(+), 4 deletions(-)
diff --git a/tools/net/ynl/lib/ynl-priv.h b/tools/net/ynl/lib/ynl-priv.h
index a8099fab035d..6cf890080dc0 100644
--- a/tools/net/ynl/lib/ynl-priv.h
+++ b/tools/net/ynl/lib/ynl-priv.h
@@ -135,6 +135,8 @@ int ynl_error_parse(struct ynl_parse_arg *yarg, const char *msg);
/* Netlink message handling helpers */
+#define YNL_MSG_OVERFLOW 1
+
static inline struct nlmsghdr *ynl_nlmsg_put_header(void *buf)
{
struct nlmsghdr *nlh = buf;
@@ -239,11 +241,29 @@ ynl_attr_first(const void *start, size_t len, size_t skip)
return ynl_attr_if_good(start + len, attr);
}
+static inline bool
+__ynl_attr_put_overflow(struct nlmsghdr *nlh, size_t size)
+{
+ bool o;
+
+ /* ynl_msg_start() stashed buffer length in nlmsg_pid. */
+ o = nlh->nlmsg_len + NLA_HDRLEN + NLMSG_ALIGN(size) > nlh->nlmsg_pid;
+ if (o)
+ /* YNL_MSG_OVERFLOW is < NLMSG_HDRLEN, all subsequent checks
+ * are guaranteed to fail.
+ */
+ nlh->nlmsg_pid = YNL_MSG_OVERFLOW;
+ return o;
+}
+
static inline struct nlattr *
ynl_attr_nest_start(struct nlmsghdr *nlh, unsigned int attr_type)
{
struct nlattr *attr;
+ if (__ynl_attr_put_overflow(nlh, 0))
+ return ynl_nlmsg_end_addr(nlh) - NLA_HDRLEN;
+
attr = ynl_nlmsg_end_addr(nlh);
attr->nla_type = attr_type | NLA_F_NESTED;
nlh->nlmsg_len += NLA_HDRLEN;
@@ -263,6 +283,9 @@ ynl_attr_put(struct nlmsghdr *nlh, unsigned int attr_type,
{
struct nlattr *attr;
+ if (__ynl_attr_put_overflow(nlh, size))
+ return;
+
attr = ynl_nlmsg_end_addr(nlh);
attr->nla_type = attr_type;
attr->nla_len = NLA_HDRLEN + size;
@@ -276,14 +299,17 @@ static inline void
ynl_attr_put_str(struct nlmsghdr *nlh, unsigned int attr_type, const char *str)
{
struct nlattr *attr;
- const char *end;
+ size_t len;
+
+ len = strlen(str);
+ if (__ynl_attr_put_overflow(nlh, len))
+ return;
attr = ynl_nlmsg_end_addr(nlh);
attr->nla_type = attr_type;
- end = stpcpy(ynl_attr_data(attr), str);
- attr->nla_len =
- NLA_HDRLEN + NLA_ALIGN(end - (char *)ynl_attr_data(attr));
+ strcpy(ynl_attr_data(attr), str);
+ attr->nla_len = NLA_HDRLEN + NLA_ALIGN(len);
nlh->nlmsg_len += NLMSG_ALIGN(attr->nla_len);
}
diff --git a/tools/net/ynl/lib/ynl.c b/tools/net/ynl/lib/ynl.c
index 484070492b17..5c9d955d0f22 100644
--- a/tools/net/ynl/lib/ynl.c
+++ b/tools/net/ynl/lib/ynl.c
@@ -404,9 +404,33 @@ struct nlmsghdr *ynl_msg_start(struct ynl_sock *ys, __u32 id, __u16 flags)
nlh->nlmsg_flags = flags;
nlh->nlmsg_seq = ++ys->seq;
+ /* This is a local YNL hack for length checking, we put the buffer
+ * length in nlmsg_pid, since messages sent to the kernel always use
+ * PID 0. Message needs to be terminated with ynl_msg_end().
+ */
+ nlh->nlmsg_pid = YNL_SOCKET_BUFFER_SIZE;
+
return nlh;
}
+static int ynl_msg_end(struct ynl_sock *ys, struct nlmsghdr *nlh)
+{
+ /* We stash buffer length in nlmsg_pid. */
+ if (nlh->nlmsg_pid == 0) {
+ yerr(ys, YNL_ERROR_INPUT_INVALID,
+ "Unknwon input buffer length");
+ return -EINVAL;
+ }
+ if (nlh->nlmsg_pid == YNL_MSG_OVERFLOW) {
+ yerr(ys, YNL_ERROR_INPUT_TOO_BIG,
+ "Constructred message longer than internal buffer");
+ return -EMSGSIZE;
+ }
+
+ nlh->nlmsg_pid = 0;
+ return 0;
+}
+
struct nlmsghdr *
ynl_gemsg_start(struct ynl_sock *ys, __u32 id, __u16 flags,
__u8 cmd, __u8 version)
@@ -607,6 +631,10 @@ static int ynl_sock_read_family(struct ynl_sock *ys, const char *family_name)
nlh = ynl_gemsg_start_req(ys, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, 1);
ynl_attr_put_str(nlh, CTRL_ATTR_FAMILY_NAME, family_name);
+ err = ynl_msg_end(ys, nlh);
+ if (err < 0)
+ return err;
+
err = send(ys->socket, nlh, nlh->nlmsg_len, 0);
if (err < 0) {
perr(ys, "failed to request socket family info");
@@ -868,6 +896,10 @@ int ynl_exec(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
{
int err;
+ err = ynl_msg_end(ys, req_nlh);
+ if (err < 0)
+ return err;
+
err = send(ys->socket, req_nlh, req_nlh->nlmsg_len, 0);
if (err < 0)
return err;
@@ -921,6 +953,10 @@ int ynl_exec_dump(struct ynl_sock *ys, struct nlmsghdr *req_nlh,
{
int err;
+ err = ynl_msg_end(ys, req_nlh);
+ if (err < 0)
+ return err;
+
err = send(ys->socket, req_nlh, req_nlh->nlmsg_len, 0);
if (err < 0)
return err;
diff --git a/tools/net/ynl/lib/ynl.h b/tools/net/ynl/lib/ynl.h
index dbeeef8ce91a..9842e85a8c57 100644
--- a/tools/net/ynl/lib/ynl.h
+++ b/tools/net/ynl/lib/ynl.h
@@ -20,6 +20,8 @@ enum ynl_error_code {
YNL_ERROR_ATTR_INVALID,
YNL_ERROR_UNKNOWN_NTF,
YNL_ERROR_INV_RESP,
+ YNL_ERROR_INPUT_INVALID,
+ YNL_ERROR_INPUT_TOO_BIG,
};
/**
--
2.44.0
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