From 15d2540e0d626b7960c9cafb3c825554fdf1a2b4 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Tue, 5 Mar 2024 10:50:00 -0800 Subject: [PATCH] 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(). Reviewed-by: Donald Hunter Link: https://lore.kernel.org/r/20240305185000.964773-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- 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..b9e77af5af5f 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, + "Unknown 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, }; /**