Описание
In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: Avoid using sk_socket after free when sending
The sk->sk_socket is not locked or referenced in backlog thread, and
during the call to skb_send_sock(), there is a race condition with
the release of sk_socket. All types of sockets(tcp/udp/unix/vsock)
will be affected.
Race conditions:
'''
CPU0 CPU1
backlog::skb_send_sock
sendmsg_unlocked
sock_sendmsg
sock_sendmsg_nosec
close(fd):
...
ops->release() -> sock_map_close()
sk_socket->ops = NULL
free(socket)
sock->ops->sendmsg
^
panic here
'''
The ref of psock become 0 after sock_map_close() executed.
'''
void sock_map_close()
{
...
if (likely(psock)) {
...
// !! here we remove psock and the ref of psock become 0
sock_map_remove_links(sk, psock)
psock = sk_psock_get(sk);
if (unlikely(!psock))
goto no_psock; <=== Control jumps here via goto
...
cancel_delayed_work_sync(&psock->work); <=== not executed
sk_psock_put(sk, psock);
...
}
'''
Based on the fact that we already wait for the workqueue to finish in
sock_map_close() if psock is held, we simply increase the psock
reference count to avoid race conditions.
With this patch, if the backlog thread is running, sock_map_close() will
wait for the backlog thread to complete and cancel all pending work.
If no backlog running, any pending work that hasn't started by then will
fail when invoked by sk_psock_get(), as the psock reference count have
been zeroed, and sk_psock_drop() will cancel all jobs via
cancel_delayed_work_sync().
In summary, we require synchronization to coordinate the backlog thread
and close() thread.
The panic I catched:
'''
Workqueue: events sk_psock_backlog
RIP: 0010:sock_sendmsg+0x21d/0x440
RAX: 0000000000000000 RBX: ffffc9000521fad8 RCX: 0000000000000001
...
Call Trace:
? die_addr+0x40/0xa0
? exc_general_protection+0x14c/0x230
? asm_exc_general_protection+0x26/0x30
? sock_sendmsg+0x21d/0x440
? sock_sendmsg+0x3e0/0x440
? __pfx_sock_sendmsg+0x10/0x10
__skb_send_sock+0x543/0xb70
sk_psock_backlog+0x247/0xb80
...
'''
A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) sockmap subsystem. A race condition exists where the sk_socket is not properly locked or referenced during the skb_send_sock() function call, allowing for a use-after-free vulnerability. This can be exploited by a local attacker, leading to a system crash (Denial of Service) and potentially enabling information disclosure or privilege escalation.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected | ||
| Red Hat Enterprise Linux 9.6 Extended Update Support | kernel | Fixed | RHSA-2026:3520 | 02.03.2026 |
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Дополнительная информация
Статус:
EPSS
7 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Avoid using sk_socket after free when sending The sk->sk_socket is not locked or referenced in backlog thread, and during the call to skb_send_sock(), there is a race condition with the release of sk_socket. All types of sockets(tcp/udp/unix/vsock) will be affected. Race conditions: ''' CPU0 CPU1 backlog::skb_send_sock sendmsg_unlocked sock_sendmsg sock_sendmsg_nosec close(fd): ... ops->release() -> sock_map_close() sk_socket->ops = NULL free(socket) sock->ops->sendmsg ^ panic here ''' The ref of psock become 0 after sock_map_close() executed. ''' void sock_map_close() { ... if (likely(psock)) { ... // !! here we remove psock and the ref of psock become 0 sock_map_remove_links(sk, psock) psock = sk_psock_get(sk); if (unlikely(!psock)) goto no_psock; <=== Control jumps here via goto ... cancel_delayed_work_sync(&psock->work); <=== not executed sk_psock_put(sk, psock); ... }...
In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Avoid using sk_socket after free when sending The sk->sk_socket is not locked or referenced in backlog thread, and during the call to skb_send_sock(), there is a race condition with the release of sk_socket. All types of sockets(tcp/udp/unix/vsock) will be affected. Race conditions: ''' CPU0 CPU1 backlog::skb_send_sock sendmsg_unlocked sock_sendmsg sock_sendmsg_nosec close(fd): ... ops->release() -> sock_map_close() sk_socket->ops = NULL free(socket) sock->ops->sendmsg ^ panic here ''' The ref of psock become 0 after sock_map_close() executed. ''' void sock_map_close() { ... if (likely(psock)) { ... // !! here we remove psock and the
In the Linux kernel, the following vulnerability has been resolved: b ...
In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Avoid using sk_socket after free when sending The sk->sk_socket is not locked or referenced in backlog thread, and during the call to skb_send_sock(), there is a race condition with the release of sk_socket. All types of sockets(tcp/udp/unix/vsock) will be affected. Race conditions: ''' CPU0 CPU1 backlog::skb_send_sock sendmsg_unlocked sock_sendmsg sock_sendmsg_nosec close(fd): ... ops->release() -> sock_map_close() sk_socket->ops = NULL free(socket) sock->ops->sendmsg ^ panic here ''' The ref of psock become 0 after sock_map_close() executed. ''' void sock_map_close() { ... if (likely(psock)) { ... // !! here we remove psock and t...
Уязвимость функции skb_send_sock() компонента BPF ядра операционной системы Linux, позволяющая нарушителю вызвать отказ в обслуживании
EPSS
7 High
CVSS3