Unrated severityNVD Advisory· Published May 27, 2026· Updated May 27, 2026

CVE-2026-45840

Description

In the Linux kernel, the following vulnerability has been resolved:

openvswitch: cap upcall PID array size and pre-size vport replies

The vport netlink reply helpers allocate a fixed-size skb with nlmsg_new(NLMSG_DEFAULT_SIZE, ...) but serialize the full upcall PID array via ovs_vport_get_upcall_portids(). Since ovs_vport_set_upcall_portids() accepts any non-zero multiple of sizeof(u32) with no upper bound, a CAP_NET_ADMIN user can install a PID array large enough to overflow the reply buffer, causing nla_put() to fail with -EMSGSIZE and hitting BUG_ON(err < 0). On systems with unprivileged user namespaces enabled (e.g., Ubuntu default), this is reachable via unshare -Urn since OVS vport mutation operations use GENL_UNS_ADMIN_PERM.

kernel BUG at net/openvswitch/datapath.c:2414! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 1 UID: 0 PID: 65 Comm: poc Not tainted 7.0.0-rc7-00195-geb216e422044 #1 RIP: 0010:ovs_vport_cmd_set+0x34c/0x400 Call Trace:

genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116) genl_rcv_msg (net/netlink/genetlink.c:1194) netlink_rcv_skb (net/netlink/af_netlink.c:2550) genl_rcv (net/netlink/genetlink.c:1219) netlink_unicast (net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Kernel panic - not syncing: Fatal exception

Reject attempts to set more PIDs than nr_cpu_ids in ovs_vport_set_upcall_portids(), and pre-compute the worst-case reply size in ovs_vport_cmd_msg_size() based on that bound, similar to the existing ovs_dp_cmd_msg_size(). nr_cpu_ids matches the cap already used by the per-CPU dispatch configuration on the datapath side (ovs_dp_cmd_fill_info() serialises at most nr_cpu_ids PIDs), so the two sides stay consistent.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

In the Linux kernel Open vSwitch (OVS), a CAP_NET_ADMIN user can trigger a kernel BUG by installing an oversized upcall PID array, causing denial of service.

Vulnerability

In the Linux kernel's Open vSwitch (OVS) module, the ovs_vport_set_upcall_portids() function accepts a user-supplied array of upcall port IDs with no upper bound on its size. The corresponding reply helpers in ovs_vport_cmd_set() allocate a fixed-size socket buffer (nlmsg_new(NLMSG_DEFAULT_SIZE)) but then serialize the entire array via ovs_vport_get_upcall_portids(). When the array exceeds the buffer capacity, nla_put() fails with -EMSGSIZE, triggering BUG_ON(err < 0) at net/openvswitch/datapath.c:2414. This was present in various kernel versions up to the fix. The commit fa6e90bc443b (backport to stable) resolves the issue by capping the PID array size to nr_cpu_ids and pre-sizing replies accordingly [1].

Exploitation

An attacker needs CAP_NET_ADMIN capability (or the ability to enter a user namespace with CAP_NET_ADMIN, e.g., via unshare -Urn on systems with unprivileged user namespaces enabled such as Ubuntu default). The attacker sends a crafted netlink message to set the upcall portids for an OVS vport, providing an array with a large number of PIDs (multiple of sizeof(u32) with no valid upper bound). This causes the reply to overflow the fixed-size buffer [1].

Impact

Successful exploitation triggers a kernel BUG (invalid opcode: 0000) leading to a kernel panic and system crash (denial of service). The attacker does not gain code execution or privilege escalation; the impact is limited to availability [1].

Mitigation

The fix is available in the Linux kernel stable tree via commit fa6e90bc443bed8dc0d55bc5ea5b27ffdfe37704 [1]. This commit caps the allowed number of PIDs to nr_cpu_ids and pre-computes the worst-case reply size accordingly. Users should apply the patch or update to a kernel version containing the fix. No workaround is available without patching. The vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog as of the publication date.

References

Making sure you're not a bot!

AI Insight generated on May 27, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

SUSE S.A./Linux Enterprise Debuginfoinferred
Range: <= 7.0.0-rc7
Ubuntu/Linux Kernelllm-fuzzy

Patches

f9ef3db77a38

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitWeiming ShiApr 16, 2026Fixed in 6.6.141via kernel-cna

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index cb52fac7caa3cd..7803e7548d9203 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2158,9 +2158,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2170,7 +2201,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 0faa6e097829c5..a0a8854e9f19e8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

2091c6aa0df6

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitWeiming ShiApr 16, 2026Fixed in 7.1-rc1via kernel-cna

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e209099218b410..bbbde50fc6498f 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2184,9 +2184,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2196,7 +2227,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 23f629e94a36ab..56b2e2d1a749f8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -406,6 +406,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

fa6e90bc443b

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitWeiming ShiApr 16, 2026Fixed in 6.18.33via kernel-cna

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index d5b6e2002bc1f6..2304c8e3be4f70 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2186,9 +2186,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2198,7 +2229,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index f0ce8ce1dce0e1..1f0c86a9f43b05 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

f99ac36b5d7c

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitWeiming ShiApr 16, 2026Fixed in 6.12.91via kernel-cna

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 8d3c01f0e2aa19..607b5ca70ea547 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2157,9 +2157,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2169,7 +2200,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 2a996858a9145b..469bc1fda726e0 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

1d6c02b86329

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitWeiming ShiApr 16, 2026Fixed in 7.0.10via kernel-cna

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e209099218b410..bbbde50fc6498f 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2184,9 +2184,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2196,7 +2227,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 23f629e94a36ab..56b2e2d1a749f8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -406,6 +406,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

f9ef3db77a38

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitWeiming ShiApr 16, 2026via nvd-ref

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index cb52fac7caa3cd..7803e7548d9203 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2158,9 +2158,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2170,7 +2201,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 0faa6e097829c5..a0a8854e9f19e8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

1d6c02b86329

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitWeiming ShiApr 16, 2026via nvd-ref

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e209099218b410..bbbde50fc6498f 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2184,9 +2184,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2196,7 +2227,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 23f629e94a36ab..56b2e2d1a749f8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -406,6 +406,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

2091c6aa0df6

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitWeiming ShiApr 16, 2026via nvd-ref

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e209099218b410..bbbde50fc6498f 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2184,9 +2184,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2196,7 +2227,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 23f629e94a36ab..56b2e2d1a749f8 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -406,6 +406,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

fa6e90bc443b

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitWeiming ShiApr 16, 2026via nvd-ref

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index d5b6e2002bc1f6..2304c8e3be4f70 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2186,9 +2186,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2198,7 +2229,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index f0ce8ce1dce0e1..1f0c86a9f43b05 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

f99ac36b5d7c

openvswitch: cap upcall PID array size and pre-size vport replies

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitWeiming ShiApr 16, 2026via nvd-ref

commit

2 files changed · +36 −3

net/openvswitch/datapath.c+33 −2 modified

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 8d3c01f0e2aa19..607b5ca70ea547 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -2157,9 +2157,40 @@ error:
 	return err;
 }
 
+static size_t ovs_vport_cmd_msg_size(void)
+{
+	size_t msgsize = NLMSG_ALIGN(sizeof(struct ovs_header));
+
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_PORT_NO */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_TYPE */
+	msgsize += nla_total_size(IFNAMSIZ);    /* OVS_VPORT_ATTR_NAME */
+	msgsize += nla_total_size(sizeof(u32)); /* OVS_VPORT_ATTR_IFINDEX */
+	msgsize += nla_total_size(sizeof(s32)); /* OVS_VPORT_ATTR_NETNSID */
+
+	/* OVS_VPORT_ATTR_STATS */
+	msgsize += nla_total_size_64bit(sizeof(struct ovs_vport_stats));
+
+	/* OVS_VPORT_ATTR_UPCALL_STATS(OVS_VPORT_UPCALL_ATTR_SUCCESS +
+	 *                             OVS_VPORT_UPCALL_ATTR_FAIL)
+	 */
+	msgsize += nla_total_size(nla_total_size_64bit(sizeof(u64)) +
+				  nla_total_size_64bit(sizeof(u64)));
+
+	/* OVS_VPORT_ATTR_UPCALL_PID */
+	msgsize += nla_total_size(nr_cpu_ids * sizeof(u32));
+
+	/* OVS_VPORT_ATTR_OPTIONS(OVS_TUNNEL_ATTR_DST_PORT +
+	 *                        OVS_TUNNEL_ATTR_EXTENSION(OVS_VXLAN_EXT_GBP))
+	 */
+	msgsize += nla_total_size(nla_total_size(sizeof(u16)) +
+				  nla_total_size(nla_total_size(0)));
+
+	return msgsize;
+}
+
 static struct sk_buff *ovs_vport_cmd_alloc_info(void)
 {
-	return nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	return genlmsg_new(ovs_vport_cmd_msg_size(), GFP_KERNEL);
 }
 
 /* Called with ovs_mutex, only via ovs_dp_notify_wq(). */
@@ -2169,7 +2200,7 @@ struct sk_buff *ovs_vport_cmd_build_info(struct vport *vport, struct net *net,
 	struct sk_buff *skb;
 	int retval;
 
-	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	skb = ovs_vport_cmd_alloc_info();
 	if (!skb)
 		return ERR_PTR(-ENOMEM);

net/openvswitch/vport.c+3 −1 modified

diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 2a996858a9145b..469bc1fda726e0 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -407,6 +407,9 @@ int ovs_vport_set_upcall_portids(struct vport *vport, const struct nlattr *ids)
 	if (!nla_len(ids) || nla_len(ids) % sizeof(u32))
 		return -EINVAL;
 
+	if (nla_len(ids) / sizeof(u32) > nr_cpu_ids)
+		return -EINVAL;
+
 	old = ovsl_dereference(vport->upcall_portids);
 
 	vport_portids = kmalloc(sizeof(*vport_portids) + nla_len(ids),
-- 
cgit 1.3-korg

Vulnerability mechanics

Root cause

"Missing upper bound check on upcall PID array size allows a buffer overflow in vport netlink reply allocation."

Attack vector

A local attacker with `CAP_NET_ADMIN` (reachable via `unshare -Urn` on systems with unprivileged user namespaces enabled) sends a crafted OVS vport set netlink message containing an oversized `OVS_VPORT_ATTR_UPCALL_PID` attribute. The function `ovs_vport_set_upcall_portids()` previously accepted any non-zero multiple of `sizeof(u32)` with no upper bound, allowing the attacker to install a PID array large enough that when `ovs_vport_get_upcall_portids()` later serializes it into a reply buffer allocated with `NLMSG_DEFAULT_SIZE`, `nla_put()` fails with `-EMSGSIZE` and triggers `BUG_ON(err

Affected code

The vulnerability resides in `net/openvswitch/vport.c` in `ovs_vport_set_upcall_portids()` and in `net/openvswitch/datapath.c` in the vport netlink reply helpers `ovs_vport_cmd_alloc_info()` and `ovs_vport_cmd_build_info()`. The former accepted an unbounded upcall PID array, and the latter allocated a fixed-size skb via `nlmsg_new(NLMSG_DEFAULT_SIZE, ...)` that could be overflowed when serializing that array [patch_id=2654207].

What the fix does

The patch applies two complementary fixes. In `net/openvswitch/vport.c`, a new bounds check rejects any PID array larger than `nr_cpu_ids` entries, preventing the oversized array from being stored [patch_id=2654207]. In `net/openvswitch/datapath.c`, the new `ovs_vport_cmd_msg_size()` function pre-computes the worst-case reply size using `nr_cpu_ids * sizeof(u32)` for the PID attribute, and `ovs_vport_cmd_alloc_info()` now calls `genlmsg_new()` with that computed size instead of the fixed `NLMSG_DEFAULT_SIZE` [patch_id=2654207]. This ensures the reply buffer is always large enough, eliminating the buffer overflow.

Preconditions

authCAP_NET_ADMIN capability (reachable via unshare -Urn on systems with unprivileged user namespaces)
configOpen vSwitch module loaded and a vport configured
networkAbility to send netlink messages to the OVS generic netlink family

Generated on May 27, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

News mentions

No linked articles in our index yet.

cvss	0.000
epss	0.000
exploit	0.000
kev	0.000
patch	-0.070
ransomware	0.000