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

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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: 0baf26b0fc ("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>
This commit is contained in:
Cen Zhang (Microsoft Security FORGE Labs)
2026-08-27 19:55:11 -04:00
committed by Jakub Kicinski
parent 5271b79b7a
commit 385e474086
2 changed files with 4 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
net/ipv4/tcp.c
View File

@@ -4561,9 +4561,11 @@ int do_tcp_getsockopt(struct sock *sk, int level,
if (copy_from_sockptr(&len, optlen, sizeof(int)))
return -EFAULT;
ca_ops = icsk->icsk_ca_ops;
rcu_read_lock();
ca_ops = READ_ONCE(icsk->icsk_ca_ops);
if (ca_ops && ca_ops->get_info)
sz = ca_ops->get_info(sk, ~0U, &attr, &info);
rcu_read_unlock();
len = min_t(unsigned int, len, sz);
if (copy_to_sockptr(optlen, &len, sizeof(int)))

2
net/ipv4/tcp_dctcp.c
View File

@@ -228,7 +228,7 @@ static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr,
if (ext & (1 << (INET_DIAG_DCTCPINFO - 1)) ||
ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
memset(&info->dctcp, 0, sizeof(info->dctcp));
if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) {
if (READ_ONCE(inet_csk(sk)->icsk_ca_ops) != &dctcp_reno) {
info->dctcp.dctcp_enabled = 1;
info->dctcp.dctcp_ce_state = (u16) ca->ce_state;
info->dctcp.dctcp_alpha = ca->dctcp_alpha;