From 3c10ffddc61f8a1a59e29a110ba70b47e679206a Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Thu, 2 Sep 2021 22:04:00 +0300 Subject: net: xfrm: fix shift-out-of-bounds in xfrm_get_default Syzbot hit shift-out-of-bounds in xfrm_get_default. The problem was in missing validation check for user data. up->dirmask comes from user-space, so we need to check if this value is less than XFRM_USERPOLICY_DIRMASK_MAX to avoid shift-out-of-bounds bugs. Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") Reported-and-tested-by: syzbot+b2be9dd8ca6f6c73ee2d@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_user.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'net/xfrm') diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 03b66d154b2b..4719a6d54aa6 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -2005,6 +2005,11 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh, return -EMSGSIZE; } + if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) { + kfree_skb(r_skb); + return -EINVAL; + } + r_up = nlmsg_data(r_nlh); r_up->action = ((net->xfrm.policy_default & (1 << up->dirmask)) >> up->dirmask); -- cgit v1.2.3-59-g8ed1b