[PATCH 3/5] xfrm: Add dir validation to "out" data path lookup

[Steffen Klassert <steffen.klassert@secunet.com>]

From: Antony Antony <antony.antony@secunet.com>

Introduces validation for the x->dir attribute within the XFRM output
data lookup path. If the configured direction does not match the expected
direction, output, increment the XfrmOutStateDirError counter and drop
the packet to ensure data integrity and correct flow handling.

grep -vw 0 /proc/net/xfrm_stat
XfrmOutPolError         	1
XfrmOutStateDirError    	1

Signed-off-by: Antony Antony <antony.antony@secunet.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---
 Documentation/networking/xfrm_proc.rst | 3 +++
 include/uapi/linux/snmp.h              | 1 +
 net/xfrm/xfrm_policy.c                 | 6 ++++++
 net/xfrm/xfrm_proc.c                   | 1 +
 4 files changed, 11 insertions(+)

diff --git a/Documentation/networking/xfrm_proc.rst b/Documentation/networking/xfrm_proc.rst
index 0a771c5a7399..5ac3acf4cf51 100644
--- a/Documentation/networking/xfrm_proc.rst
+++ b/Documentation/networking/xfrm_proc.rst
@@ -111,3 +111,6 @@ XfrmOutPolError:
 
 XfrmOutStateInvalid:
 	State is invalid, perhaps expired
+
+XfrmOutStateDirError:
+        State direction mismatch (lookup found an input state on the output path, expected output or no direction)
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index a0819c6a5988..23792b8412bd 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -337,6 +337,7 @@ enum
 	LINUX_MIB_XFRMFWDHDRERROR,		/* XfrmFwdHdrError*/
 	LINUX_MIB_XFRMOUTSTATEINVALID,		/* XfrmOutStateInvalid */
 	LINUX_MIB_XFRMACQUIREERROR,		/* XfrmAcquireError */
+	LINUX_MIB_XFRMOUTSTATEDIRERROR,		/* XfrmOutStateDirError */
 	__LINUX_MIB_XFRMMAX
 };
 
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 6affe5cd85d8..298b3a9eb48d 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2489,6 +2489,12 @@ xfrm_tmpl_resolve_one(struct xfrm_policy *policy, const struct flowi *fl,
 
 		x = xfrm_state_find(remote, local, fl, tmpl, policy, &error,
 				    family, policy->if_id);
+		if (x && x->dir && x->dir != XFRM_SA_DIR_OUT) {
+			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEDIRERROR);
+			xfrm_state_put(x);
+			error = -EINVAL;
+			goto fail;
+		}
 
 		if (x && x->km.state == XFRM_STATE_VALID) {
 			xfrm[nx++] = x;
diff --git a/net/xfrm/xfrm_proc.c b/net/xfrm/xfrm_proc.c
index 5f9bf8e5c933..98606f1078f7 100644
--- a/net/xfrm/xfrm_proc.c
+++ b/net/xfrm/xfrm_proc.c
@@ -41,6 +41,7 @@ static const struct snmp_mib xfrm_mib_list[] = {
 	SNMP_MIB_ITEM("XfrmFwdHdrError", LINUX_MIB_XFRMFWDHDRERROR),
 	SNMP_MIB_ITEM("XfrmOutStateInvalid", LINUX_MIB_XFRMOUTSTATEINVALID),
 	SNMP_MIB_ITEM("XfrmAcquireError", LINUX_MIB_XFRMACQUIREERROR),
+	SNMP_MIB_ITEM("XfrmOutStateDirError", LINUX_MIB_XFRMOUTSTATEDIRERROR),
 	SNMP_MIB_SENTINEL
 };
 
-- 
2.34.1