From: Muhammad Usama Anjum <musamaanjum@gmail.com> stable inclusion from linux-4.19.187 commit 426853f87e34c9945a655e8997d2f551b12ceb76 -------------------------------- commit 864db232dc7036aa2de19749c3d5be0143b24f8f upstream. nlh is being checked for validtity two times when it is dereferenced in this function. Check for validity again when updating the flags through nlh pointer to make the dereferencing safe. CC: <stable@vger.kernel.org> Addresses-Coverity: ("NULL pointer dereference") Signed-off-by: Muhammad Usama Anjum <musamaanjum@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- net/ipv6/route.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 800319e341783..1b37aea01a98f 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -4525,9 +4525,11 @@ static int ip6_route_multipath_add(struct fib6_config *cfg, * nexthops have been replaced by first new, the rest should * be added to it. */ - cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL | - NLM_F_REPLACE); - cfg->fc_nlinfo.nlh->nlmsg_flags |= NLM_F_CREATE; + if (cfg->fc_nlinfo.nlh) { + cfg->fc_nlinfo.nlh->nlmsg_flags &= ~(NLM_F_EXCL | + NLM_F_REPLACE); + cfg->fc_nlinfo.nlh->nlmsg_flags |= NLM_F_CREATE; + } nhn++; } -- 2.25.1