* [PATCH net 1/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)
[not found] <20260821182449.79785-1-blbllhy@gmail.com>
@ 2026-08-21 18:24 ` Cen Zhang (Microsoft)
2026-08-21 18:24 ` [PATCH net 2/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO) Cen Zhang (Microsoft)
1 sibling, 0 replies; 4+ messages in thread
From: Cen Zhang (Microsoft) @ 2026-08-21 18:24 UTC (permalink / raw)
To: edumazet, ncardwell, davem, kuba, pabeni
Cc: kuniyu, horms, yhs, kafai, andriin, ast, netdev, bpf,
linux-kernel, AutonomousCodeSecurity, xmei5, tgopinath, kys,
blbllhy, stable
do_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding
rcu_read_lock(). Since commit 0baf26b0fcd7 ("bpf: tcp: Support
tcp_congestion_ops in bpf"), icsk_ca_ops can point to dynamically
allocated BPF struct_ops memory that may be freed concurrently via
setsockopt(TCP_CONGESTION), leading to a use-after-free.
BUG: KASAN: slab-use-after-free in _copy_to_user+0x37/0x60
Read of size 16 at addr ffff888013505260 by task exploit/149
_copy_to_user+0x37/0x60
do_tcp_getsockopt+0x158a/0x2460 (net/ipv4/tcp.c:4585)
tcp_getsockopt+0x91/0xf0
__sys_getsockopt+0xf7/0x170
Fix this by holding rcu_read_lock() around the ca_ops->name access and
copying the name to a stack buffer before releasing the lock.
Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
---
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/20260416200319.3608680-1-edumazet@google.com/
net/ipv4/tcp.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b4237d0e994d..7360ff718f1d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4577,16 +4577,23 @@ int do_tcp_getsockopt(struct sock *sk, int level,
val = !inet_csk_in_pingpong_mode(sk);
break;
- case TCP_CONGESTION:
+ case TCP_CONGESTION: {
+ char ca_name[TCP_CA_NAME_MAX] = {};
+
if (copy_from_sockptr(&len, optlen, sizeof(int)))
return -EFAULT;
len = min_t(unsigned int, len, TCP_CA_NAME_MAX);
if (copy_to_sockptr(optlen, &len, sizeof(int)))
return -EFAULT;
- if (copy_to_sockptr(optval, icsk->icsk_ca_ops->name, len))
+
+ rcu_read_lock();
+ memcpy(ca_name, icsk->icsk_ca_ops->name, sizeof(ca_name));
+ rcu_read_unlock();
+
+ if (copy_to_sockptr(optval, ca_name, len))
return -EFAULT;
return 0;
-
+ }
case TCP_ULP:
if (copy_from_sockptr(&len, optlen, sizeof(int)))
return -EFAULT;
--
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH net 2/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)
[not found] <20260821182449.79785-1-blbllhy@gmail.com>
2026-08-21 18:24 ` [PATCH net 1/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) Cen Zhang (Microsoft)
@ 2026-08-21 18:24 ` Cen Zhang (Microsoft)
2026-08-21 18:39 ` Eric Dumazet
1 sibling, 1 reply; 4+ messages in thread
From: Cen Zhang (Microsoft) @ 2026-08-21 18:24 UTC (permalink / raw)
To: edumazet, ncardwell, davem, kuba, pabeni
Cc: kuniyu, horms, yhs, kafai, andriin, ast, netdev, bpf,
linux-kernel, AutonomousCodeSecurity, xmei5, tgopinath, kys,
blbllhy, stable
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: AutonomousCodeSecurity@microsoft.com
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
---
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/20260416200319.3608680-1-edumazet@google.com/
net/ipv4/tcp.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7360ff718f1d..43ccd2d37f9c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4562,9 +4562,11 @@ int do_tcp_getsockopt(struct sock *sk, int level,
if (copy_from_sockptr(&len, optlen, sizeof(int)))
return -EFAULT;
+ rcu_read_lock();
ca_ops = 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)))
--
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread