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net: xfrm: fix shift-out-of-bounds in xfrm_get_default

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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: 2d151d3907 ("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 <paskripkin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Pavel Skripkin 2021-09-02 22:04:00 +03:00 committed by Steffen Klassert
parent 626bf91a29
commit 3c10ffddc6
1 changed files with 5 additions and 0 deletions
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5
net/xfrm/xfrm_user.c
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@ -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);