Commit dbd7ae51 authored Nov 02, 2020 by Dmitry Safonov Committed by Steffen Klassert Nov 09, 2020

xfrm/compat: Translate by copying XFRMA_UNSPEC attribute



xfrm_xlate32() translates 64-bit message provided by kernel to be sent
for 32-bit listener (acknowledge or monitor). Translator code doesn't
expect XFRMA_UNSPEC attribute as it doesn't know its payload.
Kernel never attaches such attribute, but a user can.

I've searched if any opensource does it and the answer is no.
Nothing on github and google finds only tfcproject that has such code
commented-out.

What will happen if a user sends a netlink message with XFRMA_UNSPEC
attribute? Ipsec code ignores this attribute. But if there is a
monitor-process or 32-bit user requested ack - kernel will try to
translate such message and will hit WARN_ONCE() in xfrm_xlate64_attr().

Deal with XFRMA_UNSPEC by copying the attribute payload with
xfrm_nla_cpy(). In result, the default switch-case in xfrm_xlate64_attr()
becomes an unused code. Leave those 3 lines in case a new xfrm attribute
will be added.

Fixes: 5461fc0c ("xfrm/compat: Add 64=>32-bit messages translator")
Reported-by:  <syzbot+a7e701c8385bd8543074@syzkaller.appspotmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

parent 4e0396c5

net/xfrm/xfrm_compat.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -234,6 +234,7 @@ static int xfrm_xlate64_attr(struct sk_buff dst, const struct nlattr src)
		case XFRMA_PAD:
		/* Ignore */
		return 0;
		case XFRMA_UNSPEC:
		case XFRMA_ALG_AUTH:
		case XFRMA_ALG_CRYPT:
		case XFRMA_ALG_COMP:

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