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Message-ID: <20240226100020.2aa27e8f@kernel.org>
Date: Mon, 26 Feb 2024 10:00:20 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Donald Hunter <donald.hunter@...il.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
pabeni@...hat.com, jiri@...nulli.us, sdf@...gle.com,
nicolas.dichtel@...nd.com
Subject: Re: [PATCH net-next 00/15] tools: ynl: stop using libmnl
On Mon, 26 Feb 2024 09:04:12 +0000 Donald Hunter wrote:
> > On Fri, 23 Feb 2024 16:26:33 +0000 Donald Hunter wrote:
> >> Is the absence of buffer bounds checking intentional, i.e. relying on libasan?
> >
> > In ynl.c or the generated code?
>
> I'm looking at ynl_attr_nest_start() and ynl_attr_put*() in ynl-priv.h
> and there's no checks for buffer overrun. It is admittedly a big
> buffer, with rx following tx, but still.
You're right. But this series isn't making it worse, AFAIU.
We weren't checking before, we aren't checking now.
I don't want to have to add another arg to all put() calls.
How about we sash the max len on nlmsg_pid?
Something like:
diff --git a/tools/net/ynl/lib/ynl-priv.h b/tools/net/ynl/lib/ynl-priv.h
index 6361318e5c4c..d4ffe18b00f9 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 +241,26 @@ 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;
+
+ /* We stash buffer length on nlmsg_pid. */
+ o = nlh->nlmsg_len + NLA_HDRLEN + NLMSG_ALIGN(size) > nlh->nlmsg_pid;
+ if (o)
+ 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 += NLMSG_ALIGN(sizeof(struct nlattr));
@@ -263,6 +280,9 @@ 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 +296,17 @@ 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 86729119e1ef..c2ba72f68028 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 on nlmsg_pid */
+ if (nlh->nlmsg_pid == 0) {
+ yerr(ys, YNL_ERROR_INPUT_INVALID,
+ "Unknwon input buffer lenght");
+ 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)
@@ -606,6 +630,10 @@ 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");
@@ -867,6 +895,10 @@ 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;
@@ -920,6 +952,10 @@ 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,
};
/**
--
2.43.2
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