CVE-2023-53489
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-01

Last updated on: 2025-10-02

Assigner: kernel.org

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---
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Meta Information
Published
2025-10-01
Last Modified
2025-10-02
Generated
2026-05-07
AI Q&A
2025-10-01
EPSS Evaluated
2026-05-05
NVD
CVE-2023-53489
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a memory leak in the Linux kernel related to UDP and TCP sockets using zerocopy and TX timestamping features. When sending data with these options, the kernel improperly manages reference counts on socket buffers (skbs), causing a circular dependency that prevents memory from being freed when the socket is closed. This leads to leaked memory objects, as the kernel does not release all references to the socket and its buffers.


How can this vulnerability impact me? :

The vulnerability can cause memory leaks in the Linux kernel when using UDP or TCP sockets with zerocopy and TX timestamping. Over time, this can lead to increased memory usage and potential resource exhaustion on affected systems, possibly degrading system performance or causing instability.


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