tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)

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
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>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/65fd3816ed5d541d9edd4bf4fcf97104a2cf907a.1787870710.git.blbllhy@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions