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

On Fri, Aug 21, 2026 at 8:25 PM Cen Zhang (Microsoft) <[email protected]> wrote:
>
> 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().
>
> Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
> Reported-by: [email protected]
> Reported-by: Cen Zhang (Microsoft) <[email protected]>
> Cc: [email protected]
> Signed-off-by: Cen Zhang (Microsoft) <[email protected]>
> ---
> The unsynchronized icsk_ca_ops load also constitutes a data race.
> READ_ONCE()/WRITE_ONCE() annotations are intentionally left to a
> separate change; related TCP annotation work is available at:
> https://lore.kernel.org/all/[email protected]/


I don't understand.

This patch is incomplete. Please fix the remaining issues in a single
patch or series.

We have limited time; we don't want to revisit the same area  in one month.

pw-bot: cr