Patch "net: xfrm: fix shift-out-of-bounce" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: xfrm: fix shift-out-of-bounce

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-xfrm-fix-shift-out-of-bounce.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9b89a0868d94e7c306455d222bdd32b2500e0c17
Author: Pavel Skripkin <paskripkin@xxxxxxxxx>
Date:   Wed Jul 28 19:38:18 2021 +0300

    net: xfrm: fix shift-out-of-bounce
    
    [ Upstream commit 5d8dbb7fb82b8661c16d496644b931c0e2e3a12e ]
    
    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@xxxxxxxxxxxxxxxxxxxxxxxxx
    Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
    Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index b963e1acf65a..2a2c4dcb015f 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -521,6 +521,7 @@ struct xfrm_user_offload {
 #define XFRM_OFFLOAD_INBOUND	2
 
 struct xfrm_userpolicy_default {
+#define XFRM_USERPOLICY_DIRMASK_MAX	(sizeof(__u8) * 8)
 	__u8				dirmask;
 	__u8				action;
 };
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index dec24f280e83..026f29f80f88 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1919,9 +1919,14 @@ 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);