[Qemu-devel] [PULL 18/24] linux-user: don't swap NLMSG_DATA() fields

[riku.voipio@linaro.org]

From: Laurent Vivier <laurent@vivier.eu>

If the structure pointed by NLMSG_DATA() is bigger
than the size of NLMSG_DATA(), don't swap its fields
to avoid memory corruption.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/syscall.c | 72 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 42 insertions(+), 30 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index b635127..52f88e2 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -1948,29 +1948,35 @@ static abi_long host_to_target_data_route(struct nlmsghdr *nlh)
     case RTM_NEWLINK:
     case RTM_DELLINK:
     case RTM_GETLINK:
-        ifi = NLMSG_DATA(nlh);
-        ifi->ifi_type = tswap16(ifi->ifi_type);
-        ifi->ifi_index = tswap32(ifi->ifi_index);
-        ifi->ifi_flags = tswap32(ifi->ifi_flags);
-        ifi->ifi_change = tswap32(ifi->ifi_change);
-        host_to_target_link_rtattr(IFLA_RTA(ifi),
-                                   nlmsg_len - NLMSG_LENGTH(sizeof(*ifi)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*ifi))) {
+            ifi = NLMSG_DATA(nlh);
+            ifi->ifi_type = tswap16(ifi->ifi_type);
+            ifi->ifi_index = tswap32(ifi->ifi_index);
+            ifi->ifi_flags = tswap32(ifi->ifi_flags);
+            ifi->ifi_change = tswap32(ifi->ifi_change);
+            host_to_target_link_rtattr(IFLA_RTA(ifi),
+                                       nlmsg_len - NLMSG_LENGTH(sizeof(*ifi)));
+        }
         break;
     case RTM_NEWADDR:
     case RTM_DELADDR:
     case RTM_GETADDR:
-        ifa = NLMSG_DATA(nlh);
-        ifa->ifa_index = tswap32(ifa->ifa_index);
-        host_to_target_addr_rtattr(IFA_RTA(ifa),
-                                   nlmsg_len - NLMSG_LENGTH(sizeof(*ifa)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*ifa))) {
+            ifa = NLMSG_DATA(nlh);
+            ifa->ifa_index = tswap32(ifa->ifa_index);
+            host_to_target_addr_rtattr(IFA_RTA(ifa),
+                                       nlmsg_len - NLMSG_LENGTH(sizeof(*ifa)));
+        }
         break;
     case RTM_NEWROUTE:
     case RTM_DELROUTE:
     case RTM_GETROUTE:
-        rtm = NLMSG_DATA(nlh);
-        rtm->rtm_flags = tswap32(rtm->rtm_flags);
-        host_to_target_route_rtattr(RTM_RTA(rtm),
-                                    nlmsg_len - NLMSG_LENGTH(sizeof(*rtm)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*rtm))) {
+            rtm = NLMSG_DATA(nlh);
+            rtm->rtm_flags = tswap32(rtm->rtm_flags);
+            host_to_target_route_rtattr(RTM_RTA(rtm),
+                                        nlmsg_len - NLMSG_LENGTH(sizeof(*rtm)));
+        }
         break;
     default:
         return -TARGET_EINVAL;
@@ -2086,30 +2092,36 @@ static abi_long target_to_host_data_route(struct nlmsghdr *nlh)
         break;
     case RTM_NEWLINK:
     case RTM_DELLINK:
-        ifi = NLMSG_DATA(nlh);
-        ifi->ifi_type = tswap16(ifi->ifi_type);
-        ifi->ifi_index = tswap32(ifi->ifi_index);
-        ifi->ifi_flags = tswap32(ifi->ifi_flags);
-        ifi->ifi_change = tswap32(ifi->ifi_change);
-        target_to_host_link_rtattr(IFLA_RTA(ifi), nlh->nlmsg_len -
-                                   NLMSG_LENGTH(sizeof(*ifi)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*ifi))) {
+            ifi = NLMSG_DATA(nlh);
+            ifi->ifi_type = tswap16(ifi->ifi_type);
+            ifi->ifi_index = tswap32(ifi->ifi_index);
+            ifi->ifi_flags = tswap32(ifi->ifi_flags);
+            ifi->ifi_change = tswap32(ifi->ifi_change);
+            target_to_host_link_rtattr(IFLA_RTA(ifi), nlh->nlmsg_len -
+                                       NLMSG_LENGTH(sizeof(*ifi)));
+        }
         break;
     case RTM_GETADDR:
     case RTM_NEWADDR:
     case RTM_DELADDR:
-        ifa = NLMSG_DATA(nlh);
-        ifa->ifa_index = tswap32(ifa->ifa_index);
-        target_to_host_addr_rtattr(IFA_RTA(ifa), nlh->nlmsg_len -
-                                   NLMSG_LENGTH(sizeof(*ifa)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*ifa))) {
+            ifa = NLMSG_DATA(nlh);
+            ifa->ifa_index = tswap32(ifa->ifa_index);
+            target_to_host_addr_rtattr(IFA_RTA(ifa), nlh->nlmsg_len -
+                                       NLMSG_LENGTH(sizeof(*ifa)));
+        }
         break;
     case RTM_GETROUTE:
         break;
     case RTM_NEWROUTE:
     case RTM_DELROUTE:
-        rtm = NLMSG_DATA(nlh);
-        rtm->rtm_flags = tswap32(rtm->rtm_flags);
-        target_to_host_route_rtattr(RTM_RTA(rtm), nlh->nlmsg_len -
-                                    NLMSG_LENGTH(sizeof(*rtm)));
+        if (nlh->nlmsg_len >= NLMSG_LENGTH(sizeof(*rtm))) {
+            rtm = NLMSG_DATA(nlh);
+            rtm->rtm_flags = tswap32(rtm->rtm_flags);
+            target_to_host_route_rtattr(RTM_RTA(rtm), nlh->nlmsg_len -
+                                        NLMSG_LENGTH(sizeof(*rtm)));
+        }
         break;
     default:
         return -TARGET_EOPNOTSUPP;
-- 
2.1.4