net/smc: check smcd_v2_ext_offset when receiving proposal msg

When receiving proposal msg in server, the field smcd_v2_ext_offset in
proposal msg is from the remote client and can not be fully trusted.
Once the value of smcd_v2_ext_offset exceed the max value, there has
the chance to access wrong address, and crash may happen.

This patch checks the value of smcd_v2_ext_offset before using it.

Fixes: 5c21c4ccafe8 ("net/smc: determine accepted ISM devices")
Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com>
Reviewed-by: Wen Gu <guwen@linux.alibaba.com>
Reviewed-by: D. Wythe <alibuda@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5d96f9de5b5dfe252486751c6c3e6c954bd07836..6cc7b846cff1bbf35ffb2e6e22cce3b7618427f6 100644 (file)
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -2147,6 +2147,8 @@ static void smc_find_ism_v2_device_serv(struct smc_sock *new_smc,
        pclc_smcd = smc_get_clc_msg_smcd(pclc);
        smc_v2_ext = smc_get_clc_v2_ext(pclc);
        smcd_v2_ext = smc_get_clc_smcd_v2_ext(smc_v2_ext);
+       if (!pclc_smcd || !smc_v2_ext || !smcd_v2_ext)
+               goto not_found;
 
        mutex_lock(&smcd_dev_list.mutex);
        if (pclc_smcd->ism.chid) {

diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h
index 23afa4df862ed9724cf040f812e10d06e056286b..76728992541087cd8cb48a62dc56c9b4ab507fba 100644 (file)
--- a/net/smc/smc_clc.h
+++ b/net/smc/smc_clc.h
@@ -400,9 +400,15 @@ smc_get_clc_v2_ext(struct smc_clc_msg_proposal *prop)
 static inline struct smc_clc_smcd_v2_extension *
 smc_get_clc_smcd_v2_ext(struct smc_clc_v2_extension *prop_v2ext)
 {
+       u16 max_offset = offsetof(struct smc_clc_msg_proposal_area, pclc_smcd_v2_ext) -
+               offsetof(struct smc_clc_msg_proposal_area, pclc_v2_ext) -
+               offsetof(struct smc_clc_v2_extension, hdr) -
+               offsetofend(struct smc_clnt_opts_area_hdr, smcd_v2_ext_offset);
+
        if (!prop_v2ext)
                return NULL;
-       if (!ntohs(prop_v2ext->hdr.smcd_v2_ext_offset))
+       if (!ntohs(prop_v2ext->hdr.smcd_v2_ext_offset) ||
+           ntohs(prop_v2ext->hdr.smcd_v2_ext_offset) > max_offset)
                return NULL;
 
        return (struct smc_clc_smcd_v2_extension *)