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>> > >> > 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. Agreed, libmnl had the same issue. > I don't want to have to add another arg to all put() calls. > How about we sash the max len on nlmsg_pid? Seems reasonable. Minor comments below. > 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; The comment confused me here. How about "We compare against stashed buffer length in nlmsg_pid". > + if (o) > + nlh->nlmsg_pid = YNL_MSG_OVERFLOW; It took me a moment to realise that this behaves like a very short buffer length for subsequent calls to __ynl_attr_put_overflow(). Is it worth extending the comment in ynl_msg_start() to say "buffer length or overflow status"? > + 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; Is the idea here to return a struct nlattr * that is safe to use? Shouldn't we zero the values in the buffer first? > + > 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"); Typo: lenght -> 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) > @@ -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, > }; > > /**