Re: [PATCH net v3 2/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)

[Jiayuan Chen <jiayuan.chen@linux.dev>]

在 8/28/26 7:55 AM, Cen Zhang (Microsoft) wrote:
> From: "Cen Zhang (Microsoft Security FORGE Labs)" <blbllhy@gmail.com>
>
> do_tcp_getsockopt() reads icsk->icsk_ca_ops and dereferences the
> get_info function pointer without rcu_read_lock(). With BPF struct_ops
> congestion control, ca_ops can point to dynamically allocated memory
> that is freed concurrently, resulting in a use-after-free when the
> kernel dereferences or calls through the stale pointer.
>
>    BUG: KASAN: slab-use-after-free in do_tcp_getsockopt+0x2037/0x23e0
>    Read of size 8 at addr ffff888013701258 by task exploit/149
>     do_tcp_getsockopt+0x2037/0x23e0 (net/ipv4/tcp.c:4564)
>     tcp_getsockopt+0x91/0xf0
>     __sys_getsockopt+0xf7/0x170
>
> Fix this by wrapping the ca_ops load and get_info call within
> rcu_read_lock()/rcu_read_unlock(), and using READ_ONCE() to load
> the icsk_ca_ops pointer.
>
> Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
> Suggested-by: Eric Dumazet <edumazet@google.com>
> Cc: AutonomousCodeSecurity@microsoft.com
> Cc: stable@vger.kernel.org
> Assisted-by: GitHub-Copilot:claude-opus-4.6
> Reviewed-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) <blbllhy@gmail.com>


Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>