{"id":"CVE-2026-98022","revision":"ceb910e8305b43488ca32a964ec34e8a","records":[{"revision":"ceb910e8305b43488ca32a964ec34e8a","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98022","aliases":[],"title":"net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap tx_queue_len at S16_MAX to prevent oversized ring allocations\n\nSeveral subsystems allocate ring buffers sized by dev->tx_queue_len\nwith no upper bound. An unprivileged user (via unshare -Urn) can set a\nhuge tx_queue_len and exhaust global memory with ring allocations:\n\n- pfifo_fast: pfifo_fast_init() and pfifo_fast_change_tx_queue_len()\n  allocate 3 skb_array rings of tx_queue_len entries each.\n- tun: tun_queue_resize() and the queue-attach path resize ptr_rings\n  to tx_queue_len on the NETDEV_CHANGE_TX_QUEUE_LEN notifier.\n- tap (macvtap/ipvtap): tap_queue_resize() and tap_init() resize/init\n  ptr_rings to tx_queue_len on the same notifier.\n\nnetif_change_tx_queue_len() is the single entry point for IFLA_TXQLEN,\nsysfs, and the SIOCSIFTXQLEN ioctl. Cap new_len at S16_MAX (32767)\nthere so the oversized value is rejected at set time. This takes\neffect whether the device is up or down, before dev->tx_queue_len is\nwritten, before any notifier fires, and before any ring is allocated.\nThe \"> S16_MAX\" check also subsumes the previous unsigned-long\ntruncation test, and a negative ifr_qlen from the ioctl lands far\nabove the cap after conversion, so both old failure modes are covered\nby the one comparison.\n\ntx_queue_len is ambigious: both a per-ring sizing multiplier and a\ndefault queue-length/limit knob for consumers that allocate\nnothing at set time (pfifo/bfifo/gred/plug/sfb limits, htb\ndirect_qlen, qfq max_classes, teql). 32767 is chosen as the largest\nvalue NLA_POLICY_FULL_RANGE can express for the u32 IFLA_TXQLEN\npolicy in patch 2/3 while staying a legitimate queue length on\nhigh-BDP paths; the ring-memory trade-off of a shared knob is\ndisclosed below.\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.\n- Unprivileged user in a fresh user+net namespace (unshare -Urn).\n- pfifo_fast: create veth pairs, set tx_queue_len to 500000, attach\n  mq+pfifo_fast. ~28 iterations OOMs a 2GB guest.\n- tun: create 50 tun devices with IFF_MULTI_QUEUE, set tx_queue_len to\n  500000, open 8 queues each. ~1.6GB of ptr_ring allocations OOMs a\n  512MB guest.\n- tap: same as tun with IFF_TAP. ~960MB OOMs a 512MB guest.\n- On the fixed kernel the oversized tx_queue_len is rejected with\n  -ERANGE at set time (all four paths: RTM_SETLINK, RTM_NEWLINK\n  create, sysfs, ioctl - the latter two via this check, the former\n  two via this check and the 2/3 parse policy respectively).","state":0,"publishedAt":"2026-09-25T10:23:42.116+00:00","modifiedAt":"2026-10-19T09:12:27.416+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/core/dev.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"24d02c909a1725ab9eceb92db7d02e4e841f17ca\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"5e5591a0f33f7c11bf1d338dbb6c5072575de64c\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"c8d4060610c69645733c92d94fceb4b93808ac4d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"c2362c500931e5bd1826bce34e9ce28af80e7541\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"81c0e02076989743a603806a5a4f44d2c40dc01f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"081340cf70a789b94b4174af54a63ffd49677a4e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"a03b927bae4af5c23fd5315a237855c17cc8f422\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6a643ddb5624be7e0694d49f5765a8d41c1ab6d0\",\n                            \"lessThan\": \"66ab4c59b74db7ab53a1c9083feaaede393a96a0\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/core/dev.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"4.16\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"4.16\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.271\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.222\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.189\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.158\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.111\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.53\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.7\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/24d02c909a1725ab9eceb92db7d02e4e841f17ca","https://git.kernel.org/stable/c/5e5591a0f33f7c11bf1d338dbb6c5072575de64c","https://git.kernel.org/stable/c/c8d4060610c69645733c92d94fceb4b93808ac4d","https://git.kernel.org/stable/c/c2362c500931e5bd1826bce34e9ce28af80e7541","https://git.kernel.org/stable/c/81c0e02076989743a603806a5a4f44d2c40dc01f","https://git.kernel.org/stable/c/081340cf70a789b94b4174af54a63ffd49677a4e","https://git.kernel.org/stable/c/a03b927bae4af5c23fd5315a237855c17cc8f422","https://git.kernel.org/stable/c/66ab4c59b74db7ab53a1c9083feaaede393a96a0"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98022","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98022","identifiers":["CVE-2026-98022"]},"retained":false,"historicalAffected":[]}],"coverage":[]}