CVE-2023-53489
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: tcp/udp: Fix memleaks of sk and zerocopy skbs with TX timestamp. syzkaller reported [0] memory leaks of an UDP socket and ZEROCOPY skbs. We can reproduce the problem with these sequences: sk = socket(AF_INET, SOCK_DGRAM, 0) sk.setsockopt(SOL_SOCKET, SO_TIMESTAMPING, SOF_TIMESTAMPING_TX_SOFTWARE) sk.setsockopt(SOL_SOCKET, SO_ZEROCOPY, 1) sk.sendto(b'', MSG_ZEROCOPY, ('127.0.0.1', 53)) sk.close() sendmsg() calls msg_zerocopy_alloc(), which allocates a skb, sets skb->cb->ubuf.refcnt to 1, and calls sock_hold(). Here, struct ubuf_info_msgzc indirectly holds a refcnt of the socket. When the skb is sent, __skb_tstamp_tx() clones it and puts the clone into the socket's error queue with the TX timestamp. When the original skb is received locally, skb_copy_ubufs() calls skb_unclone(), and pskb_expand_head() increments skb->cb->ubuf.refcnt. This additional count is decremented while freeing the skb, but struct ubuf_info_msgzc still has a refcnt, so __msg_zerocopy_callback() is not called. The last refcnt is not released unless we retrieve the TX timestamped skb by recvmsg(). Since we clear the error queue in inet_sock_destruct() after the socket's refcnt reaches 0, there is a circular dependency. If we close() the socket holding such skbs, we never call sock_put() and leak the count, sk, and skb. TCP has the same problem, and commit e0c8bccd40fc ("net: stream: purge sk_error_queue in sk_stream_kill_queues()") tried to fix it by calling skb_queue_purge() during close(). However, there is a small chance that skb queued in a qdisc or device could be put into the error queue after the skb_queue_purge() call. In __skb_tstamp_tx(), the cloned skb should not have a reference to the ubuf to remove the circular dependency, but skb_clone() does not call skb_copy_ubufs() for zerocopy skb. So, we need to call skb_orphan_frags_rx() for the cloned skb to call skb_copy_ubufs(). [0]: BUG: memory leak unreferenced object 0xffff88800c6d2d00 (size 1152): comm "syz-executor392", pid 264, jiffies 4294785440 (age 13.044s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 cd af e8 81 00 00 00 00 ................ 02 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............ backtrace: [<0000000055636812>] sk_prot_alloc+0x64/0x2a0 net/core/sock.c:2024 [<0000000054d77b7a>] sk_alloc+0x3b/0x800 net/core/sock.c:2083 [<0000000066f3c7e0>] inet_create net/ipv4/af_inet.c:319 [inline] [<0000000066f3c7e0>] inet_create+0x31e/0xe40 net/ipv4/af_inet.c:245 [<000000009b83af97>] __sock_create+0x2ab/0x550 net/socket.c:1515 [<00000000b9b11231>] sock_create net/socket.c:1566 [inline] [<00000000b9b11231>] __sys_socket_create net/socket.c:1603 [inline] [<00000000b9b11231>] __sys_socket_create net/socket.c:1588 [inline] [<00000000b9b11231>] __sys_socket+0x138/0x250 net/socket.c:1636 [<000000004fb45142>] __do_sys_socket net/socket.c:1649 [inline] [<000000004fb45142>] __se_sys_socket net/socket.c:1647 [inline] [<000000004fb45142>] __x64_sys_socket+0x73/0xb0 net/socket.c:1647 [<0000000066999e0e>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<0000000066999e0e>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80 [<0000000017f238c1>] entry_SYSCALL_64_after_hwframe+0x63/0xcd BUG: memory leak unreferenced object 0xffff888017633a00 (size 240): comm "syz-executor392", pid 264, jiffies 4294785440 (age 13.044s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 2d 6d 0c 80 88 ff ff .........-m..... backtrace: [<000000002b1c4368>] __alloc_skb+0x229/0x320 net/core/skbuff.c:497 [<00000000143579a6>] alloc_skb include/linux/skbuff.h:1265 [inline] [<00000000143579a6>] sock_omalloc+0xaa/0x190 net/core/sock.c:2596 [<00000000be626478>] msg_zerocopy_alloc net/core/skbuff.c:1294 [inline] [<00000000be626478>] ---truncated---
View original CVE JSON
{
"id": "CVE-2023-53489",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-01T12:15:51.950",
"lastModified": "2026-11-05T21:17:23.023",
"vulnStatus": "Analyzed",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp/udp: Fix memleaks of sk and zerocopy skbs with TX timestamp.\n\nsyzkaller reported [0] memory leaks of an UDP socket and ZEROCOPY\nskbs. We can reproduce the problem with these sequences:\n\n sk = socket(AF_INET, SOCK_DGRAM, 0)\n sk.setsockopt(SOL_SOCKET, SO_TIMESTAMPING, SOF_TIMESTAMPING_TX_SOFTWARE)\n sk.setsockopt(SOL_SOCKET, SO_ZEROCOPY, 1)\n sk.sendto(b'', MSG_ZEROCOPY, ('127.0.0.1', 53))\n sk.close()\n\nsendmsg() calls msg_zerocopy_alloc(), which allocates a skb, sets\nskb->cb->ubuf.refcnt to 1, and calls sock_hold(). Here, struct\nubuf_info_msgzc indirectly holds a refcnt of the socket. When the\nskb is sent, __skb_tstamp_tx() clones it and puts the clone into\nthe socket's error queue with the TX timestamp.\n\nWhen the original skb is received locally, skb_copy_ubufs() calls\nskb_unclone(), and pskb_expand_head() increments skb->cb->ubuf.refcnt.\nThis additional count is decremented while freeing the skb, but struct\nubuf_info_msgzc still has a refcnt, so __msg_zerocopy_callback() is\nnot called.\n\nThe last refcnt is not released unless we retrieve the TX timestamped\nskb by recvmsg(). Since we clear the error queue in inet_sock_destruct()\nafter the socket's refcnt reaches 0, there is a circular dependency.\nIf we close() the socket holding such skbs, we never call sock_put()\nand leak the count, sk, and skb.\n\nTCP has the same problem, and commit e0c8bccd40fc (\"net: stream:\npurge sk_error_queue in sk_stream_kill_queues()\") tried to fix it\nby calling skb_queue_purge() during close(). However, there is a\nsmall chance that skb queued in a qdisc or device could be put\ninto the error queue after the skb_queue_purge() call.\n\nIn __skb_tstamp_tx(), the cloned skb should not have a reference\nto the ubuf to remove the circular dependency, but skb_clone() does\nnot call skb_copy_ubufs() for zerocopy skb. So, we need to call\nskb_orphan_frags_rx() for the cloned skb to call skb_copy_ubufs().\n\n[0]:\nBUG: memory leak\nunreferenced object 0xffff88800c6d2d00 (size 1152):\n comm \"syz-executor392\", pid 264, jiffies 4294785440 (age 13.044s)\n hex dump (first 32 bytes):\n 00 00 00 00 00 00 00 00 cd af e8 81 00 00 00 00 ................\n 02 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 ...@............\n backtrace:\n [<0000000055636812>] sk_prot_alloc+0x64/0x2a0 net/core/sock.c:2024\n [<0000000054d77b7a>] sk_alloc+0x3b/0x800 net/core/sock.c:2083\n [<0000000066f3c7e0>] inet_create net/ipv4/af_inet.c:319 [inline]\n [<0000000066f3c7e0>] inet_create+0x31e/0xe40 net/ipv4/af_inet.c:245\n [<000000009b83af97>] __sock_create+0x2ab/0x550 net/socket.c:1515\n [<00000000b9b11231>] sock_create net/socket.c:1566 [inline]\n [<00000000b9b11231>] __sys_socket_create net/socket.c:1603 [inline]\n [<00000000b9b11231>] __sys_socket_create net/socket.c:1588 [inline]\n [<00000000b9b11231>] __sys_socket+0x138/0x250 net/socket.c:1636\n [<000000004fb45142>] __do_sys_socket net/socket.c:1649 [inline]\n [<000000004fb45142>] __se_sys_socket net/socket.c:1647 [inline]\n [<000000004fb45142>] __x64_sys_socket+0x73/0xb0 net/socket.c:1647\n [<0000000066999e0e>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n [<0000000066999e0e>] do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80\n [<0000000017f238c1>] entry_SYSCALL_64_after_hwframe+0x63/0xcd\n\nBUG: memory leak\nunreferenced object 0xffff888017633a00 (size 240):\n comm \"syz-executor392\", pid 264, jiffies 4294785440 (age 13.044s)\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 00 00 00 00 00 00 00 2d 6d 0c 80 88 ff ff .........-m.....\n backtrace:\n [<000000002b1c4368>] __alloc_skb+0x229/0x320 net/core/skbuff.c:497\n [<00000000143579a6>] alloc_skb include/linux/skbuff.h:1265 [inline]\n [<00000000143579a6>] sock_omalloc+0xaa/0x190 net/core/sock.c:2596\n [<00000000be626478>] msg_zerocopy_alloc net/core/skbuff.c:1294 [inline]\n [<00000000be626478>]\n---truncated---"
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