kernel/linux.git/net/openvswitch/flow_netlink.c, branch v6.19.11

openvswitch: validate MPLS set/set_masked payload length

2026-04-02T11:25:26+00:00

[ Upstream commit 546b68ac893595877ffbd7751e5c55fd1c43ede6 ] validate_set() accepted OVS_KEY_ATTR_MPLS as variable-sized payload for SET/SET_MASKED actions. In action handling, OVS expects fixed-size MPLS key data (struct ovs_key_mpls). Use the already normalized key_len (masked case included) and reject non-matching MPLS action key sizes. Reject invalid MPLS action payload lengths early. Fixes: fbdcdd78da7c ("Change in Openvswitch to support MPLS label depth of 3 in ingress direction") Reported-by: Yifan Wu Reported-by: Juefei Pu Tested-by: Ao Zhou Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Signed-off-by: Yang Yang Reviewed-by: Ilya Maximets Link: https://patch.msgid.link/20260319080228.3423307-1-n05ec@lzu.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: openvswitch: fix middle attribute validation in push_nsh() action

2025-12-10T08:46:55+00:00

The push_nsh() action structure looks like this: OVS_ACTION_ATTR_PUSH_NSH(OVS_KEY_ATTR_NSH(OVS_NSH_KEY_ATTR_BASE,...)) The outermost OVS_ACTION_ATTR_PUSH_NSH attribute is OK'ed by the nla_for_each_nested() inside __ovs_nla_copy_actions(). The innermost OVS_NSH_KEY_ATTR_BASE/MD1/MD2 are OK'ed by the nla_for_each_nested() inside nsh_key_put_from_nlattr(). But nothing checks if the attribute in the middle is OK. We don't even check that this attribute is the OVS_KEY_ATTR_NSH. We just do a double unwrap with a pair of nla_data() calls - first time directly while calling validate_push_nsh() and the second time as part of the nla_for_each_nested() macro, which isn't safe, potentially causing invalid memory access if the size of this attribute is incorrect. The failure may not be noticed during validation due to larger netlink buffer, but cause trouble later during action execution where the buffer is allocated exactly to the size: BUG: KASAN: slab-out-of-bounds in nsh_hdr_from_nlattr+0x1dd/0x6a0 [openvswitch] Read of size 184 at addr ffff88816459a634 by task a.out/22624 CPU: 8 UID: 0 PID: 22624 6.18.0-rc7+ #115 PREEMPT(voluntary) Call Trace: dump_stack_lvl+0x51/0x70 print_address_description.constprop.0+0x2c/0x390 kasan_report+0xdd/0x110 kasan_check_range+0x35/0x1b0 __asan_memcpy+0x20/0x60 nsh_hdr_from_nlattr+0x1dd/0x6a0 [openvswitch] push_nsh+0x82/0x120 [openvswitch] do_execute_actions+0x1405/0x2840 [openvswitch] ovs_execute_actions+0xd5/0x3b0 [openvswitch] ovs_packet_cmd_execute+0x949/0xdb0 [openvswitch] genl_family_rcv_msg_doit+0x1d6/0x2b0 genl_family_rcv_msg+0x336/0x580 genl_rcv_msg+0x9f/0x130 netlink_rcv_skb+0x11f/0x370 genl_rcv+0x24/0x40 netlink_unicast+0x73e/0xaa0 netlink_sendmsg+0x744/0xbf0 __sys_sendto+0x3d6/0x450 do_syscall_64+0x79/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Let's add some checks that the attribute is properly sized and it's the only one attribute inside the action. Technically, there is no real reason for OVS_KEY_ATTR_NSH to be there, as we know that we're pushing an NSH header already, it just creates extra nesting, but that's how uAPI works today. So, keeping as it is. Fixes: b2d0f5d5dc53 ("openvswitch: enable NSH support") Reported-by: Junvy Yang Signed-off-by: Ilya Maximets Acked-by: Eelco Chaudron echaudro@redhat.com Reviewed-by: Aaron Conole Link: https://patch.msgid.link/20251204105334.900379-1-i.maximets@ovn.org Signed-off-by: Jakub Kicinski

net: openvswitch: remove never-working support for setting nsh fields

2025-11-15T02:13:24+00:00

The validation of the set(nsh(...)) action is completely wrong. It runs through the nsh_key_put_from_nlattr() function that is the same function that validates NSH keys for the flow match and the push_nsh() action. However, the set(nsh(...)) has a very different memory layout. Nested attributes in there are doubled in size in case of the masked set(). That makes proper validation impossible. There is also confusion in the code between the 'masked' flag, that says that the nested attributes are doubled in size containing both the value and the mask, and the 'is_mask' that says that the value we're parsing is the mask. This is causing kernel crash on trying to write into mask part of the match with SW_FLOW_KEY_PUT() during validation, while validate_nsh() doesn't allocate any memory for it: BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1c2383067 P4D 1c2383067 PUD 20b703067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 8 UID: 0 Kdump: loaded Not tainted 6.17.0-rc4+ #107 PREEMPT(voluntary) RIP: 0010:nsh_key_put_from_nlattr+0x19d/0x610 [openvswitch] Call Trace: validate_nsh+0x60/0x90 [openvswitch] validate_set.constprop.0+0x270/0x3c0 [openvswitch] __ovs_nla_copy_actions+0x477/0x860 [openvswitch] ovs_nla_copy_actions+0x8d/0x100 [openvswitch] ovs_packet_cmd_execute+0x1cc/0x310 [openvswitch] genl_family_rcv_msg_doit+0xdb/0x130 genl_family_rcv_msg+0x14b/0x220 genl_rcv_msg+0x47/0xa0 netlink_rcv_skb+0x53/0x100 genl_rcv+0x24/0x40 netlink_unicast+0x280/0x3b0 netlink_sendmsg+0x1f7/0x430 ____sys_sendmsg+0x36b/0x3a0 ___sys_sendmsg+0x87/0xd0 __sys_sendmsg+0x6d/0xd0 do_syscall_64+0x7b/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e The third issue with this process is that while trying to convert the non-masked set into masked one, validate_set() copies and doubles the size of the OVS_KEY_ATTR_NSH as if it didn't have any nested attributes. It should be copying each nested attribute and doubling them in size independently. And the process must be properly reversed during the conversion back from masked to a non-masked variant during the flow dump. In the end, the only two outcomes of trying to use this action are either validation failure or a kernel crash. And if somehow someone manages to install a flow with such an action, it will most definitely not do what it is supposed to, since all the keys and the masks are mixed up. Fixing all the issues is a complex task as it requires re-writing most of the validation code. Given that and the fact that this functionality never worked since introduction, let's just remove it altogether. It's better to re-introduce it later with a proper implementation instead of trying to fix it in stable releases. Fixes: b2d0f5d5dc53 ("openvswitch: enable NSH support") Reported-by: Junvy Yang Signed-off-by: Ilya Maximets Acked-by: Eelco Chaudron Reviewed-by: Aaron Conole Link: https://patch.msgid.link/20251112112246.95064-1-i.maximets@ovn.org Signed-off-by: Jakub Kicinski

openvswitch: Stricter validation for the userspace action

2025-05-15T02:13:34+00:00

This change enhances the robustness of validate_userspace() by ensuring that all Netlink attributes are fully contained within the parent attribute. The previous use of nla_parse_nested_deprecated() could silently skip trailing or malformed attributes, as it stops parsing at the first invalid entry. By switching to nla_parse_deprecated_strict(), we make sure only fully validated attributes are copied for later use. Signed-off-by: Eelco Chaudron Reviewed-by: Simon Horman Acked-by: Ilya Maximets Link: https://patch.msgid.link/67eb414e2d250e8408bb8afeb982deca2ff2b10b.1747037304.git.echaudro@redhat.com Signed-off-by: Jakub Kicinski

net: openvswitch: fix nested key length validation in the set() action

2025-04-14T23:15:38+00:00

It's not safe to access nla_len(ovs_key) if the data is smaller than the netlink header. Check that the attribute is OK first. Fixes: ccb1352e76cf ("net: Add Open vSwitch kernel components.") Reported-by: syzbot+b07a9da40df1576b8048@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b07a9da40df1576b8048 Tested-by: syzbot+b07a9da40df1576b8048@syzkaller.appspotmail.com Signed-off-by: Ilya Maximets Reviewed-by: Eelco Chaudron Acked-by: Aaron Conole Link: https://patch.msgid.link/20250412104052.2073688-1-i.maximets@ovn.org Signed-off-by: Jakub Kicinski

net: openvswitch: remove misbehaving actions length check

2025-03-13T09:29:18+00:00

The actions length check is unreliable and produces different results depending on the initial length of the provided netlink attribute and the composition of the actual actions inside of it. For example, a user can add 4088 empty clone() actions without triggering -EMSGSIZE, on attempt to add 4089 such actions the operation will fail with the -EMSGSIZE verdict. However, if another 16 KB of other actions will be *appended* to the previous 4089 clone() actions, the check passes and the flow is successfully installed into the openvswitch datapath. The reason for a such a weird behavior is the way memory is allocated. When ovs_flow_cmd_new() is invoked, it calls ovs_nla_copy_actions(), that in turn calls nla_alloc_flow_actions() with either the actual length of the user-provided actions or the MAX_ACTIONS_BUFSIZE. The function adds the size of the sw_flow_actions structure and then the actually allocated memory is rounded up to the closest power of two. So, if the user-provided actions are larger than MAX_ACTIONS_BUFSIZE, then MAX_ACTIONS_BUFSIZE + sizeof(*sfa) rounded up is 32K + 24 -> 64K. Later, while copying individual actions, we look at ksize(), which is 64K, so this way the MAX_ACTIONS_BUFSIZE check is not actually triggered and the user can easily allocate almost 64 KB of actions. However, when the initial size is less than MAX_ACTIONS_BUFSIZE, but the actions contain ones that require size increase while copying (such as clone() or sample()), then the limit check will be performed during the reserve_sfa_size() and the user will not be allowed to create actions that yield more than 32 KB internally. This is one part of the problem. The other part is that it's not actually possible for the userspace application to know beforehand if the particular set of actions will be rejected or not. Certain actions require more space in the internal representation, e.g. an empty clone() takes 4 bytes in the action list passed in by the user, but it takes 12 bytes in the internal representation due to an extra nested attribute, and some actions require less space in the internal representations, e.g. set(tunnel(..)) normally takes 64+ bytes in the action list provided by the user, but only needs to store a single pointer in the internal implementation, since all the data is stored in the tunnel_info structure instead. And the action size limit is applied to the internal representation, not to the action list passed by the user. So, it's not possible for the userpsace application to predict if the certain combination of actions will be rejected or not, because it is not possible for it to calculate how much space these actions will take in the internal representation without knowing kernel internals. All that is causing random failures in ovs-vswitchd in userspace and inability to handle certain traffic patterns as a result. For example, it is reported that adding a bit more than a 1100 VMs in an OpenStack setup breaks the network due to OVS not being able to handle ARP traffic anymore in some cases (it tries to install a proper datapath flow, but the kernel rejects it with -EMSGSIZE, even though the action list isn't actually that large.) Kernel behavior must be consistent and predictable in order for the userspace application to use it in a reasonable way. ovs-vswitchd has a mechanism to re-direct parts of the traffic and partially handle it in userspace if the required action list is oversized, but that doesn't work properly if we can't actually tell if the action list is oversized or not. Solution for this is to check the size of the user-provided actions instead of the internal representation. This commit just removes the check from the internal part because there is already an implicit size check imposed by the netlink protocol. The attribute can't be larger than 64 KB. Realistically, we could reduce the limit to 32 KB, but we'll be risking to break some existing setups that rely on the fact that it's possible to create nearly 64 KB action lists today. Vast majority of flows in real setups are below 100-ish bytes. So removal of the limit will not change real memory consumption on the system. The absolutely worst case scenario is if someone adds a flow with 64 KB of empty clone() actions. That will yield a 192 KB in the internal representation consuming 256 KB block of memory. However, that list of actions is not meaningful and also a no-op. Real world very large action lists (that can occur for a rare cases of BUM traffic handling) are unlikely to contain a large number of clones and will likely have a lot of tunnel attributes making the internal representation comparable in size to the original action list. So, it should be fine to just remove the limit. Commit in the 'Fixes' tag is the first one that introduced the difference between internal representation and the user-provided action lists, but there were many more afterwards that lead to the situation we have today. Fixes: 7d5437c709de ("openvswitch: Add tunneling interface.") Signed-off-by: Ilya Maximets Reviewed-by: Aaron Conole Link: https://patch.msgid.link/20250308004609.2881861-1-i.maximets@ovn.org Signed-off-by: Paolo Abeni

net: convert to nla_get_*_default()

2024-11-11T18:32:06+00:00

Most of the original conversion is from the spatch below, but I edited some and left out other instances that were either buggy after conversion (where default values don't fit into the type) or just looked strange. @@ expression attr, def; expression val; identifier fn =~ "^nla_get_.*"; fresh identifier dfn = fn ## "_default"; @@ ( -if (attr) - val = fn(attr); -else - val = def; +val = dfn(attr, def); | -if (!attr) - val = def; -else - val = fn(attr); +val = dfn(attr, def); | -if (!attr) - return def; -return fn(attr); +return dfn(attr, def); | -attr ? fn(attr) : def +dfn(attr, def) | -!attr ? def : fn(attr) +dfn(attr, def) ) Signed-off-by: Johannes Berg Reviewed-by: Toke Høiland-Jørgensen Link: https://patch.msgid.link/20241108114145.0580b8684e7f.I740beeaa2f70ebfc19bfca1045a24d6151992790@changeid Signed-off-by: Jakub Kicinski

net: openvswitch: Use ERR_CAST() to return

2024-08-30T18:11:45+00:00

Using ERR_CAST() is more reasonable and safer, When it is necessary to convert the type of an error pointer and return it. Signed-off-by: Yan Zhen Acked-by: Eelco Chaudron Reviewed-by: Aaron Conole Link: https://patch.msgid.link/20240829095509.3151987-1-yanzhen@vivo.com Signed-off-by: Jakub Kicinski

net: openvswitch: add psample action

2024-07-06T00:45:47+00:00

Add support for a new action: psample. This action accepts a u32 group id and a variable-length cookie and uses the psample multicast group to make the packet available for observability. The maximum length of the user-defined cookie is set to 16, same as tc_cookie, to discourage using cookies that will not be offloadable. Reviewed-by: Michal Kubiak Reviewed-by: Aaron Conole Reviewed-by: Ilya Maximets Acked-by: Eelco Chaudron Signed-off-by: Adrian Moreno Link: https://patch.msgid.link/20240704085710.353845-6-amorenoz@redhat.com Signed-off-by: Jakub Kicinski

ip_tunnel: convert __be16 tunnel flags to bitmaps

2024-04-01T09:49:28+00:00

Historically, tunnel flags like TUNNEL_CSUM or TUNNEL_ERSPAN_OPT have been defined as __be16. Now all of those 16 bits are occupied and there's no more free space for new flags. It can't be simply switched to a bigger container with no adjustments to the values, since it's an explicit Endian storage, and on LE systems (__be16)0x0001 equals to (__be64)0x0001000000000000. We could probably define new 64-bit flags depending on the Endianness, i.e. (__be64)0x0001 on BE and (__be64)0x00010000... on LE, but that would introduce an Endianness dependency and spawn a ton of Sparse warnings. To mitigate them, all of those places which were adjusted with this change would be touched anyway, so why not define stuff properly if there's no choice. Define IP_TUNNEL_*_BIT counterparts as a bit number instead of the value already coded and a fistful of <16 <-> bitmap> converters and helpers. The two flags which have a different bit position are SIT_ISATAP_BIT and VTI_ISVTI_BIT, as they were defined not as __cpu_to_be16(), but as (__force __be16), i.e. had different positions on LE and BE. Now they both have strongly defined places. Change all __be16 fields which were used to store those flags, to IP_TUNNEL_DECLARE_FLAGS() -> DECLARE_BITMAP(__IP_TUNNEL_FLAG_NUM) -> unsigned long[1] for now, and replace all TUNNEL_* occurrences to their bitmap counterparts. Use the converters in the places which talk to the userspace, hardware (NFP) or other hosts (GRE header). The rest must explicitly use the new flags only. This must be done at once, otherwise there will be too many conversions throughout the code in the intermediate commits. Finally, disable the old __be16 flags for use in the kernel code (except for the two 'irregular' flags mentioned above), to prevent any accidental (mis)use of them. For the userspace, nothing is changed, only additions were made. Most noticeable bloat-o-meter difference (.text): vmlinux: 307/-1 (306) gre.ko: 62/0 (62) ip_gre.ko: 941/-217 (724) [*] ip_tunnel.ko: 390/-900 (-510) [**] ip_vti.ko: 138/0 (138) ip6_gre.ko: 534/-18 (516) [*] ip6_tunnel.ko: 118/-10 (108) [*] gre_flags_to_tnl_flags() grew, but still is inlined [**] ip_tunnel_find() got uninlined, hence such decrease The average code size increase in non-extreme case is 100-200 bytes per module, mostly due to sizeof(long) > sizeof(__be16), as %__IP_TUNNEL_FLAG_NUM is less than %BITS_PER_LONG and the compilers are able to expand the majority of bitmap_*() calls here into direct operations on scalars. Reviewed-by: Simon Horman Signed-off-by: Alexander Lobakin Signed-off-by: David S. Miller