{"cve":"CVE-2023-53685","nvd":{"published":"2025-10-07T16:15:52.777","modified":"2026-10-28T19:10:00.193","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntun: Fix memory leak for detached NAPI queue.\n\nsyzkaller reported [0] memory leaks of sk and skb related to the TUN\ndevice with no repro, but we can reproduce it easily with:\n\n  struct ifreq ifr = {}\n  int fd_tun, fd_tmp;\n  char buf[4] = {};\n\n  fd_tun = openat(AT_FDCWD, \"/dev/net/tun\", O_WRONLY, 0);\n  ifr.ifr_flags = IFF_TUN | IFF_NAPI | IFF_MULTI_QUEUE;\n  ioctl(fd_tun, TUNSETIFF, &ifr);\n\n  ifr.ifr_flags = IFF_DETACH_QUEUE;\n  ioctl(fd_tun, TUNSETQUEUE, &ifr);\n\n  fd_tmp = socket(AF_PACKET, SOCK_PACKET, 0);\n  ifr.ifr_flags = IFF_UP;\n  ioctl(fd_tmp, SIOCSIFFLAGS, &ifr);\n\n  write(fd_tun, buf, sizeof(buf));\n  close(fd_tun);\n\nIf we enable NAPI and multi-queue on a TUN device, we can put skb into\ntfile->sk.sk_write_queue after the queue is detached.  We should prevent\nit by checking tfile->detached before queuing skb.\n\nNote this must be done under tfile->sk.sk_write_queue.lock because write()\nand ioctl(IFF_DETACH_QUEUE) can run concurrently.  Otherwise, there would\nbe a small race window:\n\n  write()                             ioctl(IFF_DETACH_QUEUE)\n  `- tun_get_user                     `- __tun_detach\n     |- if (tfile->detached)             |- tun_disable_queue\n     |  `-> false                        |  `- tfile->detached = tun\n     |                                   `- tun_queue_purge\n     |- spin_lock_bh(&queue->lock)\n     `- __skb_queue_tail(queue, skb)\n\nAnother solution is to call tun_queue_purge() when closing and\nreattaching the detached queue, but it could paper over another\nproblems.  Also, we do the same kind of test for IFF_NAPI_FRAGS.\n\n[0]:\nunreferenced object 0xffff88801edbc800 (size 2048):\n  comm \"syz-executor.1\", pid 33269, jiffies 4295743834 (age 18.756s)\n  hex dump (first 32 bytes):\n    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................\n    00 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............\n  backtrace:\n    [<000000008c16ea3d>] __do_kmalloc_node mm/slab_common.c:965 [inline]\n    [<000000008c16ea3d>] __kmalloc+0x4a/0x130 mm/slab_common.c:979\n    [<000000003addde56>] kmalloc include/linux/slab.h:563 [inline]\n    [<000000003addde56>] sk_prot_alloc+0xef/0x1b0 net/core/sock.c:2035\n    [<000000003e20621f>] sk_alloc+0x36/0x2f0 net/core/sock.c:2088\n    [<0000000028e43843>] tun_chr_open+0x3d/0x190 drivers/net/tun.c:3438\n    [<000000001b0f1f28>] misc_open+0x1a6/0x1f0 drivers/char/misc.c:165\n    [<000000004376f706>] chrdev_open+0x111/0x300 fs/char_dev.c:414\n    [<00000000614d379f>] do_dentry_open+0x2f9/0x750 fs/open.c:920\n    [<000000008eb24774>] do_open fs/namei.c:3636 [inline]\n    [<000000008eb24774>] path_openat+0x143f/0x1a30 fs/namei.c:3791\n    [<00000000955077b5>] do_filp_open+0xce/0x1c0 fs/namei.c:3818\n    [<00000000b78973b0>] do_sys_openat2+0xf0/0x260 fs/open.c:1356\n    [<00000000057be699>] do_sys_open fs/open.c:1372 [inline]\n    [<00000000057be699>] __do_sys_openat fs/open.c:1388 [inline]\n    [<00000000057be699>] __se_sys_openat fs/open.c:1383 [inline]\n    [<00000000057be699>] __x64_sys_openat+0x83/0xf0 fs/open.c:1383\n    [<00000000a7d2182d>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n    [<00000000a7d2182d>] do_syscall_64+0x3c/0x90 arch/x86/entry/common.c:80\n    [<000000004cc4e8c4>] entry_SYSCALL_64_after_hwframe+0x72/0xdc\n\nunreferenced object 0xffff88802f671700 (size 240):\n  comm \"syz-executor.1\", pid 33269, jiffies 4295743854 (age 18.736s)\n  hex dump (first 32 bytes):\n    68 c9 db 1e 80 88 ff ff 68 c9 db 1e 80 88 ff ff  h.......h.......\n    00 c0 7b 2f 80 88 ff ff 00 c8 db 1e 80 88 ff ff  ..{/............\n  backtrace:\n    [<00000000e9d9fdb6>] __alloc_skb+0x223/0x250 net/core/skbuff.c:644\n    [<000000002c3e4e0b>] alloc_skb include/linux/skbuff.h:1288 [inline]\n    [<000000002c3e4e0b>] alloc_skb_with_frags+0x6f/0x350 net/core/skbuff.c:6378\n    [<00000000825f98d7>] sock_alloc_send_pskb+0x3ac/0x3e0 net/core/sock.c:2729\n    [<00000000e9eb3df3>] tun_alloc_skb drivers/net/tun.c:1529 [inline]\n    [<\n---truncated---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-401"],"references":["https://git.kernel.org/stable/c/0d20210a190f76db9ec35ee4e0fc77e6c7a148f5","https://git.kernel.org/stable/c/82b2bc279467c875ec36f8ef820f00997c2a4e8e","https://git.kernel.org/stable/c/9cae243b9ae25adfe468cd47ceca591f6725b79c"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-28T19:37:43.506563291+00:00"},"epss":{"cve":"CVE-2023-53685","score":0.00146,"percentile":0.03852,"date":"2026-10-28"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}