* FAILED: patch "[PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)" failed to apply to 5.15-stable tree
@ 2026-10-21 17:57 gregkh
2026-10-22 19:19 ` [PATCH 5.15.y] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: gregkh @ 2026-10-21 17:57 UTC (permalink / raw)
To: blbllhy, edumazet, jiayuan.chen, kuba, leitao, matttbe, xmei5; +Cc: stable
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 5271b79b7ad68dcb222e893773f92bdabf7750f3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026102127-crept-debate-2807@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5271b79b7ad68dcb222e893773f92bdabf7750f3 Mon Sep 17 00:00:00 2001
From: "Cen Zhang (Microsoft Security FORGE Labs)" <blbllhy@gmail.com>
Date: Thu, 27 Aug 2026 19:55:10 -0400
Subject: [PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)
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,
using READ_ONCE() to load icsk_ca_ops, and copying the name to a
stack buffer before releasing the lock. Also annotate the relevant
icsk_ca_ops stores with WRITE_ONCE() to fix the accompanying KCSAN
data-race issue.
Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
Suggested-by: Eric Dumazet <edumazet@google.com>
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Link: https://lore.kernel.org/all/20260821182449.79785-2-blbllhy@gmail.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>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/d3f97f1acbf0010898148be6e6406e4b8b4a5c84.1787870710.git.blbllhy@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 93d723d8c109..740999c9efff 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4576,16 +4576,24 @@ 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, READ_ONCE(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;
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index e9f6c77e0631..8e83ef81fc18 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -223,7 +223,7 @@ void tcp_assign_congestion_control(struct sock *sk)
ca = rcu_dereference(net->ipv4.tcp_congestion_control);
if (unlikely(!bpf_try_module_get(ca, ca->owner)))
ca = &tcp_reno;
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
rcu_read_unlock();
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
@@ -253,7 +253,7 @@ static void tcp_reinit_congestion_control(struct sock *sk,
struct inet_connection_sock *icsk = inet_csk(sk);
tcp_cleanup_congestion_control(sk);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
icsk->icsk_ca_setsockopt = 1;
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index 274e628e7cf8..99f68c2992d0 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -111,7 +111,7 @@ __bpf_kfunc static void dctcp_init(struct sock *sk)
/* No ECN support? Fall back to Reno. Also need to clear
* ECT from sk since it is set during 3WHS for DCTCP.
*/
- inet_csk(sk)->icsk_ca_ops = &dctcp_reno;
+ WRITE_ONCE(inet_csk(sk)->icsk_ca_ops, &dctcp_reno);
INET_ECN_dontxmit(sk);
}
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index f3fa0b18eda0..0ddfd5af6e58 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -507,7 +507,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
ca = tcp_ca_find_key(ca_key);
if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
ca_got_dst = true;
}
rcu_read_unlock();
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index c5ffffee4349..d960e3de7d50 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4092,7 +4092,7 @@ static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
}
rcu_read_unlock();
}
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH 5.15.y] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)
2026-10-21 17:57 FAILED: patch "[PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)" failed to apply to 5.15-stable tree gregkh
@ 2026-10-22 19:19 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-10-22 19:19 UTC (permalink / raw)
To: stable
Cc: Cen Zhang (Microsoft Security FORGE Labs), Eric Dumazet,
Xiang Mei (Microsoft), AutonomousCodeSecurity, Jiayuan Chen,
Matthieu Baerts (NGI0), Breno Leitao, Jakub Kicinski, Sasha Levin
From: "Cen Zhang (Microsoft Security FORGE Labs)" <blbllhy@gmail.com>
[ Upstream commit 5271b79b7ad68dcb222e893773f92bdabf7750f3 ]
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,
using READ_ONCE() to load icsk_ca_ops, and copying the name to a
stack buffer before releasing the lock. Also annotate the relevant
icsk_ca_ops stores with WRITE_ONCE() to fix the accompanying KCSAN
data-race issue.
Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
Suggested-by: Eric Dumazet <edumazet@google.com>
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Link: https://lore.kernel.org/all/20260821182449.79785-2-blbllhy@gmail.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>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/d3f97f1acbf0010898148be6e6406e4b8b4a5c84.1787870710.git.blbllhy@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ sashal: Replaced socket-pointer helpers with the existing get_user(), put_user(), and copy_to_user() APIs. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/tcp.c | 14 +++++++++++---
net/ipv4/tcp_cong.c | 4 ++--
net/ipv4/tcp_dctcp.c | 2 +-
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv4/tcp_output.c | 2 +-
5 files changed, 16 insertions(+), 8 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5e1c3ad6d1c5e..990afe964c9c2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4070,16 +4070,24 @@ static 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 (get_user(len, optlen))
return -EFAULT;
len = min_t(unsigned int, len, TCP_CA_NAME_MAX);
if (put_user(len, optlen))
return -EFAULT;
- if (copy_to_user(optval, icsk->icsk_ca_ops->name, len))
+
+ rcu_read_lock();
+ memcpy(ca_name, READ_ONCE(icsk->icsk_ca_ops)->name,
+ sizeof(ca_name));
+ rcu_read_unlock();
+
+ if (copy_to_user(optval, ca_name, len))
return -EFAULT;
return 0;
-
+ }
case TCP_ULP:
if (get_user(len, optlen))
return -EFAULT;
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index f43db30a7195d..3c3b6e1ab5424 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -164,7 +164,7 @@ void tcp_assign_congestion_control(struct sock *sk)
ca = rcu_dereference(net->ipv4.tcp_congestion_control);
if (unlikely(!bpf_try_module_get(ca, ca->owner)))
ca = &tcp_reno;
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
rcu_read_unlock();
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
@@ -194,7 +194,7 @@ static void tcp_reinit_congestion_control(struct sock *sk,
struct inet_connection_sock *icsk = inet_csk(sk);
tcp_cleanup_congestion_control(sk);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
icsk->icsk_ca_setsockopt = 1;
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index ef7a8d810265f..654e502cf1b31 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -106,7 +106,7 @@ static void dctcp_init(struct sock *sk)
/* No ECN support? Fall back to Reno. Also need to clear
* ECT from sk since it is set during 3WHS for DCTCP.
*/
- inet_csk(sk)->icsk_ca_ops = &dctcp_reno;
+ WRITE_ONCE(inet_csk(sk)->icsk_ca_ops, &dctcp_reno);
INET_ECN_dontxmit(sk);
}
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index be4fb0ce2574c..a2ec0bbac6a1a 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -416,7 +416,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
ca = tcp_ca_find_key(ca_key);
if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
ca_got_dst = true;
}
rcu_read_unlock();
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7ebd8c88d2ab3..c32a1bf2016ce 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3680,7 +3680,7 @@ static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst)
if (likely(ca && bpf_try_module_get(ca, ca->owner))) {
bpf_module_put(icsk->icsk_ca_ops, icsk->icsk_ca_ops->owner);
icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst);
- icsk->icsk_ca_ops = ca;
+ WRITE_ONCE(icsk->icsk_ca_ops, ca);
}
rcu_read_unlock();
}
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-10-22 19:19 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-10-21 17:57 FAILED: patch "[PATCH] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)" failed to apply to 5.15-stable tree gregkh
2026-10-22 19:19 ` [PATCH 5.15.y] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) Sasha Levin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox