From 5d8dbb7fb82b8661c16d496644b931c0e2e3a12e Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Wed, 28 Jul 2021 19:38:18 +0300 Subject: net: xfrm: fix shift-out-of-bounce We need to check up->dirmask to avoid shift-out-of-bounce bug, since up->dirmask comes from userspace. Also, added XFRM_USERPOLICY_DIRMASK_MAX constant to uapi to inform user-space that up->dirmask has maximum possible value Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy") Reported-and-tested-by: syzbot+9cd5837a045bbee5b810@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_user.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'net/xfrm') diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 4eafd1130c3e..127c99f71c99 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1966,9 +1966,14 @@ static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh, { struct net *net = sock_net(skb->sk); struct xfrm_userpolicy_default *up = nlmsg_data(nlh); - u8 dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK; + u8 dirmask; u8 old_default = net->xfrm.policy_default; + if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) + return -EINVAL; + + dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK; + net->xfrm.policy_default = (old_default & (0xff ^ dirmask)) | (up->action << up->dirmask); -- cgit