In the Linux kernel, the following vulnerability has been resolved: tls: fix missing memory barrier in tls_init In tls_init(), a write memory barrier is missing, and store-store reordering may cause NULL dereference in tls_{setsockopt,…

Overview

In the Linux kernel, the following vulnerability has been resolved:

tls: fix missing memory barrier in tls_init

In tls_init(), a write memory barrier is missing, and store-store reordering may cause NULL dereference in tls_{setsockopt,getsockopt}.

CPU0 CPU1

// In tls_init() // In tls_ctx_create() ctx = kzalloc() ctx->sk_proto = READ_ONCE(sk->sk_prot) -(1)

// In update_sk_prot() WRITE_ONCE(sk->sk_prot, tls_prots) -(2)

                               // In sock_common_setsockopt()
                               READ_ONCE(sk->sk_prot)->setsockopt()

                               // In tls_{setsockopt,getsockopt}()
                               ctx->sk_proto->setsockopt()    -(3)

In the above scenario, when (1) and (2) are reordered, (3) can observe the NULL value of ctx->sk_proto, causing NULL dereference.

To fix it, we rely on rcu_assign_pointer() which implies the release barrier semantic. By moving rcu_assign_pointer() after ctx->sk_proto is initialized, we can ensure that ctx->sk_proto are visible when changing sk->sk_prot.

Affected

• linux_kernel >= 5.7, < 5.10.219
• linux_kernel >= 5.11, < 5.15.161
• linux_kernel >= 5.16, < 6.1.93
• linux_kernel >= 6.2, < 6.6.33
• linux_kernel >= 6.7, < 6.9.4

Remediation

Upgrade past the affected range:

• linux_kernel 6.9.4