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[46.138.187.224]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-3a60767aa6asm6220941fa.40.2026.09.19.06.43.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 06:43:50 -0700 (PDT) From: Artem Lytkin To: netdev@vger.kernel.org Cc: bridge@lists.linux.dev, razor@blackwall.org, idosch@nvidia.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, andrew+netdev@lunn.ch, kuniyu@google.com, michael.chan@broadcom.com, pavan.chebbi@broadcom.com, ajit.khaparde@broadcom.com, sriharsha.basavapatna@broadcom.com, anthony.l.nguyen@intel.com, przemyslaw.kitszel@intel.com, intel-wired-lan@lists.osuosl.org, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, oss-drivers@corigine.com, wintera@linux.ibm.com, aswin@linux.ibm.com, linux-s390@vger.kernel.org Subject: [PATCH net-next v3 2/2] net: bridge: fail link info that does not fit in a netlink attribute Date: Sat, 19 Sep 2026 16:43:33 +0300 Message-ID: <20260919134333.49379-3-iprintercanon@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260919134333.49379-1-iprintercanon@gmail.com> References: <20260919134333.49379-1-iprintercanon@gmail.com> Precedence: bulk X-Mailing-List: bridge@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit nla_len is a u16, and a port with enough VLANs, tunnels or MST entries makes the IFLA_AF_SPEC nest wrap, so userspace reads garbage. Same for the inner MST and CFM nests. Use nla_nest_end_safe() for all three and return -E2BIG with an extack on overflow. Dumps end with that error, notifications go through rtnl_set_sk_err() so listeners resync. Assisted-by: Claude:claude-opus-5 Signed-off-by: Artem Lytkin --- net/bridge/br_netlink.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index 855a46aec3a89..fbd91b86d4268 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -459,7 +459,7 @@ static int br_fill_ifinfo(struct sk_buff *skb, const struct net_bridge_port *port, u32 pid, u32 seq, int event, unsigned int flags, u32 filter_mask, const struct net_device *dev, - bool getlink) + bool getlink, struct netlink_ext_ack *extack) { u8 operstate = netif_running(dev) ? READ_ONCE(dev->operstate) : IF_OPER_DOWN; @@ -588,7 +588,8 @@ static int br_fill_ifinfo(struct sk_buff *skb, goto nla_put_failure; } - nla_nest_end(skb, cfm_nest); + if (nla_nest_end_safe(skb, cfm_nest) < 0) + goto nla_nest_too_large; } if ((filter_mask & RTEXT_FILTER_MST) && @@ -608,20 +609,27 @@ static int br_fill_ifinfo(struct sk_buff *skb, if (err) goto nla_put_failure; - nla_nest_end(skb, mst_nest); + if (nla_nest_end_safe(skb, mst_nest) < 0) + goto nla_nest_too_large; } done: if (af) { - if (nlmsg_get_pos(skb) - (void *)af > nla_attr_size(0)) - nla_nest_end(skb, af); - else + if (nla_nest_end_safe(skb, af) < 0) + goto nla_nest_too_large; + if (!nla_len(af)) nla_nest_cancel(skb, af); } nlmsg_end(skb, nlh); return 0; +nla_nest_too_large: + NL_SET_ERR_MSG_MOD(extack, + "AF_SPEC info too large, use per-object dumps (e.g. RTM_GETVLAN)"); + nlmsg_cancel(skb, nlh); + return -E2BIG; + nla_put_failure: nlmsg_cancel(skb, nlh); return -EMSGSIZE; @@ -654,7 +662,8 @@ void br_info_notify(int event, const struct net_bridge *br, if (skb == NULL) goto errout; - err = br_fill_ifinfo(skb, port, 0, 0, event, 0, filter, dev, false); + err = br_fill_ifinfo(skb, port, 0, 0, event, 0, filter, dev, false, + NULL); if (err < 0) { /* -EMSGSIZE implies BUG in br_nlmsg_size() */ WARN_ON(err == -EMSGSIZE); @@ -693,7 +702,7 @@ int br_getlink(struct sk_buff *skb, u32 pid, u32 seq, return 0; return br_fill_ifinfo(skb, port, pid, seq, RTM_NEWLINK, nlflags, - filter_mask, dev, true); + filter_mask, dev, true, extack); } static int br_vlan_info(struct net_bridge *br, struct net_bridge_port *p, -- 2.43.0