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CVE-2026-98276

net: lock the socket in sock_gettstamp()

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: net: lock the socket in sock_gettstamp() sk->sk_flags must only be changed while holding the socket lock, because sock_set_flag() and sock_reset_flag() use non atomic operations (__set_bit() and __clear_bit()). sock_gettstamp() is one of the last places where a bit of sk->sk_flags is changed from a syscall without owning the socket lock, through sock_enable_timestamp(sk, SOCK_TIMESTAMP). sk_set_memalloc() and sk_clear_memalloc() also change sk->sk_flags without the socket lock, but their callers (nbd, iscsi_tcp, nvme-tcp, sunrpc, wireguard) need a careful audit, this will be addressed in a separate patch. Jungwoo Lee and Wongi Lee reported an UDP socket use-after-free caused by this bug: a SIOCGSTAMPNS_NEW ioctl racing with bind() can cancel the SOCK_RCU_FREE bit that udp_lib_get_port() just set, because both threads perform a read-modify-write on the same word. CPU 0 (bind) CPU 1 (SIOCGSTAMPNS_NEW) -------------------------------- ---------------------------- read sk_flags = F read sk_flags = F compute F | BIT(SOCK_RCU_FREE) compute F | BIT(SOCK_TIMESTAMP) store F | BIT(SOCK_RCU_FREE) sk_add_node_rcu(sk, ...) store F | BIT(SOCK_TIMESTAMP) After the lost update, SOCK_RCU_FREE is clear while the socket is visible to lockless UDP receive lookups. sk_destruct() then frees the socket immediately instead of waiting for a RCU grace period, while the receive path still holds a reference-less pointer to it: BUG: KASAN: slab-use-after-free in ipv4_pktinfo_prepare+0x30/0x410 Read of size 8 at addr ffff888008806610 by task exploit/207 CPU: 0 UID: 1000 PID: 207 Comm: exploit Not tainted 6.12.95+ #1 ipv4_pktinfo_prepare+0x30/0x410 udp_queue_rcv_one_skb+0x51c/0x1180 udp_unicast_rcv_skb+0x109/0x350 ip_protocol_deliver_rcu+0x14b/0x310 ip_local_deliver_finish+0x29d/0x390 ip_local_deliver+0x24d/0x2a0 Only grab the socket lock when SOCK_TIMESTAMP has to be set, to keep the common case lockless.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 18899e2e4023369a8f7739c2255a59a9748d8d17; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 88c804847dd87dc613b771b392ccecdb94725032; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 3b12d3967e96f1b7b977d9fc352ae29a1b299a82; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 17b2a1eb97fdb2a2cbaeab3b146b26797ea9311f; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 1f73253add8365d0dad0a4f421acaa8c21d20cef; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in d9f96bc2d822501f84d1caa6275a2c6b316ca2c4; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 899650bbf985b7bfd2a7b808357df9b16e6d6959; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 9ed55f3dbef4f4adfe65eb03b0c35c53229a8490

  • Linux Linux

    2.6.12

  • KernelLinux

    From 2.6.12 · fixed in 5.10.271; From 5.11.0 · fixed in 5.15.222; From 5.16.0 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.54; From 6.19.0 · fixed in 7.2.8

References 8

git.kernel.org