netdev - [PATCH ipsec] xfrm: validate new SA's prefixlen using SA family when sel.family is unset

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Message-ID: <c8e8f0326a3993792a65125fa200965e8a4580e4.1727795385.git.sd@queasysnail.net>
Date: Tue,  1 Oct 2024 18:48:14 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: netdev@...r.kernel.org
Cc: steffen.klassert@...unet.com,
	Sabrina Dubroca <sd@...asysnail.net>,
	syzbot+cc39f136925517aed571@...kaller.appspotmail.com
Subject: [PATCH ipsec] xfrm: validate new SA's prefixlen using SA family when sel.family is unset

This expands the validation introduced in commit 07bf7908950a ("xfrm:
Validate address prefix lengths in the xfrm selector.")

syzbot created an SA with
    usersa.sel.family = AF_UNSPEC
    usersa.sel.prefixlen_s = 128
    usersa.family = AF_INET

Because of the AF_UNSPEC selector, verify_newsa_info doesn't put
limits on prefixlen_{s,d}. But then copy_from_user_state sets
x->sel.family to usersa.family (AF_INET). Do the same conversion in
verify_newsa_info before validating prefixlen_{s,d}, since that's how
prefixlen is going to be used later on.

Reported-by: syzbot+cc39f136925517aed571@...kaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/xfrm/xfrm_user.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 55f039ec3d59..8d06a37adbd9 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -201,6 +201,7 @@ static int verify_newsa_info(struct xfrm_usersa_info *p,
 {
 	int err;
 	u8 sa_dir = attrs[XFRMA_SA_DIR] ? nla_get_u8(attrs[XFRMA_SA_DIR]) : 0;
+	u16 family = p->sel.family;
 
 	err = -EINVAL;
 	switch (p->family) {
@@ -221,7 +222,10 @@ static int verify_newsa_info(struct xfrm_usersa_info *p,
 		goto out;
 	}
 
-	switch (p->sel.family) {
+	if (!family && !(p->flags & XFRM_STATE_AF_UNSPEC))
+		family = p->family;
+
+	switch (family) {
 	case AF_UNSPEC:
 		break;
 
-- 
2.45.2