Too big userdata could overflow netlink message leading to out-of-bound memory accesses or assertion while formatting nested actions.
Fix that by checking the saize and returning correct error code. Credit to OSS-Fuzz. Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27640 Fixes: e995e3df57ea ("Allow OVS_USERSPACE_ATTR_USERDATA to be variable length.") Signed-off-by: Ilya Maximets <[email protected]> --- lib/odp-util.c | 30 +++++++++++++++++++++-------- lib/odp-util.h | 10 +++++----- ofproto/ofproto-dpif-xlate.c | 12 ++++++------ tests/odp.at | 37 ++++++++++++++++++++++++++++++++++++ 4 files changed, 70 insertions(+), 19 deletions(-) diff --git a/lib/odp-util.c b/lib/odp-util.c index 252a91bfa..879dea97e 100644 --- a/lib/odp-util.c +++ b/lib/odp-util.c @@ -1455,14 +1455,20 @@ parse_odp_userspace_action(const char *s, struct ofpbuf *actions) int n1 = -1; if (ovs_scan(&s[n], ",tunnel_out_port=%"SCNi32")%n", &tunnel_out_port, &n1)) { - odp_put_userspace_action(pid, user_data, user_data_size, - tunnel_out_port, include_actions, actions); - res = n + n1; + res = odp_put_userspace_action(pid, user_data, user_data_size, + tunnel_out_port, include_actions, + actions); + if (res >= 0) { + res = n + n1; + } goto out; } else if (s[n] == ')') { - odp_put_userspace_action(pid, user_data, user_data_size, - ODPP_NONE, include_actions, actions); - res = n + 1; + res = odp_put_userspace_action(pid, user_data, user_data_size, + ODPP_NONE, include_actions, + actions); + if (res >= 0) { + res = n + 1; + } goto out; } } @@ -7559,8 +7565,10 @@ odp_key_fitness_to_string(enum odp_key_fitness fitness) * Netlink PID 'pid'. If 'userdata' is nonnull, adds a userdata attribute * whose contents are the 'userdata_size' bytes at 'userdata' and returns the * offset within 'odp_actions' of the start of the cookie. (If 'userdata' is - * null, then the return value is not meaningful.) */ -size_t + * null, then the return value is not meaningful.) + * + * Returns negative error code on failure. */ +int odp_put_userspace_action(uint32_t pid, const void *userdata, size_t userdata_size, odp_port_t tunnel_out_port, @@ -7573,6 +7581,9 @@ odp_put_userspace_action(uint32_t pid, offset = nl_msg_start_nested(odp_actions, OVS_ACTION_ATTR_USERSPACE); nl_msg_put_u32(odp_actions, OVS_USERSPACE_ATTR_PID, pid); if (userdata) { + if (nl_attr_oversized(userdata_size)) { + return -E2BIG; + } userdata_ofs = odp_actions->size + NLA_HDRLEN; /* The OVS kernel module before OVS 1.11 and the upstream Linux kernel @@ -7598,6 +7609,9 @@ odp_put_userspace_action(uint32_t pid, if (include_actions) { nl_msg_put_flag(odp_actions, OVS_USERSPACE_ATTR_ACTIONS); } + if (nl_attr_oversized(odp_actions->size - offset - NLA_HDRLEN)) { + return -E2BIG; + } nl_msg_end_nested(odp_actions, offset); return userdata_ofs; diff --git a/lib/odp-util.h b/lib/odp-util.h index 623a66aa2..46593c411 100644 --- a/lib/odp-util.h +++ b/lib/odp-util.h @@ -356,11 +356,11 @@ struct user_action_cookie { }; BUILD_ASSERT_DECL(sizeof(struct user_action_cookie) == 48); -size_t odp_put_userspace_action(uint32_t pid, - const void *userdata, size_t userdata_size, - odp_port_t tunnel_out_port, - bool include_actions, - struct ofpbuf *odp_actions); +int odp_put_userspace_action(uint32_t pid, + const void *userdata, size_t userdata_size, + odp_port_t tunnel_out_port, + bool include_actions, + struct ofpbuf *odp_actions); void odp_put_tunnel_action(const struct flow_tnl *tunnel, struct ofpbuf *odp_actions, const char *tnl_type); diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c index 11aa20754..9171290e0 100644 --- a/ofproto/ofproto-dpif-xlate.c +++ b/ofproto/ofproto-dpif-xlate.c @@ -3222,12 +3222,12 @@ compose_sample_action(struct xlate_ctx *ctx, odp_port_t odp_port = ofp_port_to_odp_port( ctx->xbridge, ctx->xin->flow.in_port.ofp_port); uint32_t pid = dpif_port_get_pid(ctx->xbridge->dpif, odp_port); - size_t cookie_offset = odp_put_userspace_action(pid, cookie, - sizeof *cookie, - tunnel_out_port, - include_actions, - ctx->odp_actions); - + ssize_t cookie_offset = odp_put_userspace_action(pid, cookie, + sizeof *cookie, + tunnel_out_port, + include_actions, + ctx->odp_actions); + ovs_assert(cookie_offset >= 0); if (is_sample) { nl_msg_end_nested(ctx->odp_actions, actions_offset); nl_msg_end_nested(ctx->odp_actions, sample_offset); diff --git a/tests/odp.at b/tests/odp.at index 1ebdf0515..0fa644620 100644 --- a/tests/odp.at +++ b/tests/odp.at @@ -398,6 +398,43 @@ odp_actions_from_string: error ]) AT_CLEANUP +AT_SETUP([OVS datapath actions parsing and formatting - userdata overflow]) +dnl Userdata should fit in a single netlink message, i.e. should be less than +dnl UINT16_MAX - NLA_HDRLEN = 65535 - 4 = 65531 bytes. OVS should not accept +dnl larger userdata. OTOH, userdata is pat of a nested netlink message, that +dnl should not be oversized too. 'pid' takes NLA_HDRLEN + 4 = 8 bytes. +dnl Plus NLA_HDRLEN for the nested header. 'actions' flag takes NLA_HDRLEN = 4 +dnl and 'tunnel_out_port' takes NLA_HDRLEN + 4 = 8 bytes. +dnl So, for the variant with 'actions' maximum length of userdata should be: +dnl UINT16_MAX - NLA_HDRLEN - (NLA_HDRLEN + 4) - NLA_HDRLEN - NLA_HDRLEN +dnl total max nested header pid actions userdata +dnl Result: 65515 bytes for the actual userdata. +dnl For the case with 'tunnel_out_port': 65511 +dnl Size of userdata will be rounded up to be multiple of 4, so highest +dnl aceptable sizes are 65512 and 65508. + +dnl String with length 65512 * 2 = 131024 is valid, while 131026 is not. +data_valid=$( printf '%*s' 131024 | tr ' ' "a") +data_invalid=$(printf '%*s' 131026 | tr ' ' "a") + +echo "userspace(pid=1234567,userdata(${data_valid}),actions)" > actions.txt +echo "userspace(pid=1234567,userdata(${data_invalid}),actions)" >> actions.txt + +dnl String with length 65508 * 2 = 131016 is valid, while 131018 is not. +data_valid=$( printf '%*s' 131016 | tr ' ' "a") +data_invalid=$(printf '%*s' 131018 | tr ' ' "a") + +echo "userspace(pid=1234567,userdata(${data_valid}),tunnel_out_port=10)" >> actions.txt +echo "userspace(pid=1234567,userdata(${data_invalid}),tunnel_out_port=10)" >> actions.txt + +AT_CHECK_UNQUOTED([ovstest test-odp parse-actions < actions.txt], [0], [dnl +`cat actions.txt | head -1` +odp_actions_from_string: error +`cat actions.txt | head -3 | tail -1` +odp_actions_from_string: error +]) +AT_CLEANUP + AT_SETUP([OVS datapath keys parsing and formatting - 33 nested encap ]) AT_DATA([odp-in.txt], [dnl encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap(encap())))))))))))))))))))))))))))))))) -- 2.25.4 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
