From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4543637C0FD; Tue, 24 Mar 2026 10:00:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774346460; cv=none; b=PU+Pb/AvoNbZkuxL9UU0FmQfbIqhc/NzNYOJEyd2nElPJpf5vei+Z1yPx1ZYvm6PVJVA7L5kGVOKU1zLuPOVZPLhgYFZoIzQOA1NJI4hBXMC2hdtRq+pefZgJT0rNkOkFPR9ncrxbID17QEBMMOEZorbc1limIrSe3pUdO/U3Eo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774346460; c=relaxed/simple; bh=uqI/fe+VQ0ECJLNh7ED9MIIYVDOciSY4Pq2+0eFQATg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S46zDtd48Pmcklk3qM0+vyNuVbK4XcJV1LTTNW56yB7fV5DctmIckBwG+DEEcdJ+8KB79mPKfXmzVwSPZuL9n47YxYUyx58okWnpVu0GEfiSA3VENSuErIdhomV5ADBQ8ehSXf6GoflW/VfyBPvvE8MBE33VP7PXHCOEffQebBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qP9TSKSA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qP9TSKSA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B5DA4C19424; Tue, 24 Mar 2026 10:00:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774346459; bh=uqI/fe+VQ0ECJLNh7ED9MIIYVDOciSY4Pq2+0eFQATg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qP9TSKSAVL2kuWeyBl+1YC35rectpuSZL1ULd/wsrNUoBtpOtuEZWr3VPt9vssWTS 0IY547sWw3A/mB3r1xeESYK97KCmnmXxJW0a0i0TJEjnZXQi+Eqw1hNIPFnFYTNiip yRAvThSPyJtiU3R+tRr9CiRVV2hB+zqE2gcwE8QYUGSGSRf5m0/17+VX9VOcrRYDcX R60u46u4id6CPdSfTpl38Rx84iqPzNQsu+DRoUozAo8kpVEJnlcEWAp1SMoUWYkz+8 VCv6eagZjpBQD0hDlRAquBaH7UgNB7TLMBOMuhRVhjqd9hBU42Ye0RjuFnvdz8jM2G G4jvrfAPOTgMA== Message-ID: Date: Tue, 24 Mar 2026 11:00:54 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH 6.6 438/567] net: use dst_dev_rcu() in sk_setup_caps() To: Greg Kroah-Hartman , stable@vger.kernel.org Cc: patches@lists.linux.dev, edumazet@google.com, kuniyu@google.com, kuba@kernel.org, dsahern@kernel.org, netdev@vger.kernel.org, Ruohan Lan , Eric Dumazet , David Ahern , Jakub Kicinski References: <20260323134533.749096647@linuxfoundation.org> <20260323134544.788448840@linuxfoundation.org> From: Matthieu Baerts Content-Language: fr Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Greg, Ruohan, On 23/03/2026 14:45, Greg Kroah-Hartman wrote: > 6.6-stable review patch. If anyone has any objections, please let me know. I do! > ------------------ > > From: Eric Dumazet > > [ Upstream commit 99a2ace61b211b0be861b07fbaa062fca4b58879 ] > > Use RCU to protect accesses to dst->dev from sk_setup_caps() > and sk_dst_gso_max_size(). > > Also use dst_dev_rcu() in ip6_dst_mtu_maybe_forward(), > and ip_dst_mtu_maybe_forward(). > > ip4_dst_hoplimit() can use dst_dev_net_rcu(). > > Fixes: 4a6ce2b6f2ec ("net: introduce a new function dst_dev_put()") > Signed-off-by: Eric Dumazet > Reviewed-by: David Ahern > Link: https://patch.msgid.link/20250828195823.3958522-6-edumazet@google.com > Signed-off-by: Jakub Kicinski > [ Adjust context ] It looks like more adjustments are required: with this patch, running the MPTCP 'diag.sh' selftest using kernel/configs/debug.config causes this warning: ============================= WARNING: suspicious RCU usage 6.6.129 #1 Tainted: G N ----------------------------- include/net/dst.h:577 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by mptcp_connect/213: #0: ffff88810f9b0130 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_stream_connect (net/ipv4/af_inet.c:747) #1: ffff88810fe28130 (k-sk_lock-AF_INET#2){+.+.}-{0:0}, at: mptcp_connect (net/mptcp/protocol.c:3883) stack backtrace: CPU: 3 PID: 213 Comm: mptcp_connect Tainted: G N 6.6.129 #1 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: dump_stack_lvl (lib/dump_stack.c:107) lockdep_rcu_suspicious (include/linux/context_tracking.h:153) ip_dst_mtu_maybe_forward.constprop.0 (include/net/dst.h:577 (discriminator 13)) ? __build_flow_key.constprop.0 (include/net/ip.h:457) ? __lock_acquire (kernel/locking/lockdep.c:5719) ? tcp_mtup_init (net/ipv4/tcp_output.c:1779 (discriminator 4)) tcp_connect_init (net/ipv4/tcp_output.c:3804 (discriminator 1)) ? tcp_sync_mss (net/ipv4/tcp_output.c:3786) ? ipv4_dst_check (net/ipv4/route.c:1232) ? __sk_dst_check (net/core/sock.c:601 (discriminator 2)) ? inet_sk_rebuild_header (net/ipv4/af_inet.c:1316) ? reacquire_held_locks (kernel/locking/lockdep.c:5405) ? __lock_acquire (kernel/locking/lockdep.c:5719) tcp_connect (net/ipv4/tcp_output.c:3986) ? mark_held_locks (kernel/locking/lockdep.c:4274 (discriminator 1)) ? tcp_send_syn_data (net/ipv4/tcp_output.c:3974) ? trace_hardirqs_on (kernel/trace/trace_preemptirq.c:62 (discriminator 1)) tcp_v4_connect (net/ipv4/tcp_ipv4.c:335 (discriminator 1)) ? trace_tcp_bad_csum (net/ipv4/tcp_ipv4.c:214) mptcp_connect (net/mptcp/protocol.c:3892) __inet_stream_connect (net/ipv4/af_inet.c:676) ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300) inet_stream_connect (net/ipv4/af_inet.c:748) __sys_connect (net/socket.c:2056 (discriminator 2)) ? __sys_connect_file (net/socket.c:2063) ? update_socket_protocol+0x10/0x10 __x64_sys_connect (net/socket.c:2083 (discriminator 1)) ? syscall_enter_from_user_mode (arch/x86/include/asm/irqflags.h:42) do_syscall_64 (arch/x86/entry/common.c:46 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) RIP: 0033:0x7f2b23041186 Code: 47 ba 04 00 00 00 48 8b 05 87 3c 19 00 64 89 10 48 c7 c2 ff ff ff ff c9 48 89 d0 c3 0f 1f 84 00 00 00 00 00 48 8b 45 10 0f 05 <48> 89 c2 48 3d 00 f0 ff ff 77 0f c9 48 89 d0 c3 66 2e 0f 1f 84 00 All code ======== 0: 47 ba 04 00 00 00 rex.RXB mov $0x4,%r10d 6: 48 8b 05 87 3c 19 00 mov 0x193c87(%rip),%rax # 0x193c94 d: 64 89 10 mov %edx,%fs:(%rax) 10: 48 c7 c2 ff ff ff ff mov $0xffffffffffffffff,%rdx 17: c9 leave 18: 48 89 d0 mov %rdx,%rax 1b: c3 ret 1c: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 23: 00 24: 48 8b 45 10 mov 0x10(%rbp),%rax 28: 0f 05 syscall 2a:* 48 89 c2 mov %rax,%rdx <-- trapping instruction 2d: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 33: 77 0f ja 0x44 35: c9 leave 36: 48 89 d0 mov %rdx,%rax 39: c3 ret 3a: 66 data16 3b: 2e cs 3c: 0f .byte 0xf 3d: 1f (bad) 3e: 84 00 test %al,(%rax) Code starting with the faulting instruction =========================================== 0: 48 89 c2 mov %rax,%rdx 3: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 9: 77 0f ja 0x1a b: c9 leave c: 48 89 d0 mov %rdx,%rax f: c3 ret 10: 66 data16 11: 2e cs 12: 0f .byte 0xf 13: 1f (bad) 14: 84 00 test %al,(%rax) RSP: 002b:00007fff4638afa0 EFLAGS: 00000202 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f2b23041186 RDX: 0000000000000010 RSI: 0000557a15fd7360 RDI: 0000000000000003 RBP: 00007fff4638afb0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000106 R13: 000000000000000a R14: 00007f2b2328a000 R15: 0000557a15fd7330 ============================= WARNING: suspicious RCU usage 6.6.129 #1 Tainted: G N ----------------------------- include/net/net_namespace.h:411 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by mptcp_connect/213: #0: ffff88810f9b0130 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_stream_connect (net/ipv4/af_inet.c:747) #1: ffff88810fe28130 (k-sk_lock-AF_INET#2){+.+.}-{0:0}, at: mptcp_connect (net/mptcp/protocol.c:3883) stack backtrace: CPU: 3 PID: 213 Comm: mptcp_connect Tainted: G N 6.6.129 #1 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: dump_stack_lvl (lib/dump_stack.c:107) lockdep_rcu_suspicious (include/linux/context_tracking.h:153) ip_dst_mtu_maybe_forward.constprop.0 (include/net/net_namespace.h:411 (discriminator 13)) ? __build_flow_key.constprop.0 (include/net/ip.h:457) ? __lock_acquire (kernel/locking/lockdep.c:5719) ? tcp_mtup_init (net/ipv4/tcp_output.c:1779 (discriminator 4)) tcp_connect_init (net/ipv4/tcp_output.c:3804 (discriminator 1)) ? tcp_sync_mss (net/ipv4/tcp_output.c:3786) ? ipv4_dst_check (net/ipv4/route.c:1232) ? __sk_dst_check (net/core/sock.c:601 (discriminator 2)) ? inet_sk_rebuild_header (net/ipv4/af_inet.c:1316) ? reacquire_held_locks (kernel/locking/lockdep.c:5405) ? __lock_acquire (kernel/locking/lockdep.c:5719) tcp_connect (net/ipv4/tcp_output.c:3986) ? mark_held_locks (kernel/locking/lockdep.c:4274 (discriminator 1)) ? tcp_send_syn_data (net/ipv4/tcp_output.c:3974) ? trace_hardirqs_on (kernel/trace/trace_preemptirq.c:62 (discriminator 1)) tcp_v4_connect (net/ipv4/tcp_ipv4.c:335 (discriminator 1)) ? trace_tcp_bad_csum (net/ipv4/tcp_ipv4.c:214) mptcp_connect (net/mptcp/protocol.c:3892) __inet_stream_connect (net/ipv4/af_inet.c:676) ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300) inet_stream_connect (net/ipv4/af_inet.c:748) __sys_connect (net/socket.c:2056 (discriminator 2)) ? __sys_connect_file (net/socket.c:2063) ? update_socket_protocol+0x10/0x10 __x64_sys_connect (net/socket.c:2083 (discriminator 1)) ? syscall_enter_from_user_mode (arch/x86/include/asm/irqflags.h:42) do_syscall_64 (arch/x86/entry/common.c:46 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) RIP: 0033:0x7f2b23041186 Code: 47 ba 04 00 00 00 48 8b 05 87 3c 19 00 64 89 10 48 c7 c2 ff ff ff ff c9 48 89 d0 c3 0f 1f 84 00 00 00 00 00 48 8b 45 10 0f 05 <48> 89 c2 48 3d 00 f0 ff ff 77 0f c9 48 89 d0 c3 66 2e 0f 1f 84 00 All code ======== 0: 47 ba 04 00 00 00 rex.RXB mov $0x4,%r10d 6: 48 8b 05 87 3c 19 00 mov 0x193c87(%rip),%rax # 0x193c94 d: 64 89 10 mov %edx,%fs:(%rax) 10: 48 c7 c2 ff ff ff ff mov $0xffffffffffffffff,%rdx 17: c9 leave 18: 48 89 d0 mov %rdx,%rax 1b: c3 ret 1c: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1) 23: 00 24: 48 8b 45 10 mov 0x10(%rbp),%rax 28: 0f 05 syscall 2a:* 48 89 c2 mov %rax,%rdx <-- trapping instruction 2d: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 33: 77 0f ja 0x44 35: c9 leave 36: 48 89 d0 mov %rdx,%rax 39: c3 ret 3a: 66 data16 3b: 2e cs 3c: 0f .byte 0xf 3d: 1f (bad) 3e: 84 00 test %al,(%rax) Code starting with the faulting instruction =========================================== 0: 48 89 c2 mov %rax,%rdx 3: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax 9: 77 0f ja 0x1a b: c9 leave c: 48 89 d0 mov %rdx,%rax f: c3 ret 10: 66 data16 11: 2e cs 12: 0f .byte 0xf 13: 1f (bad) 14: 84 00 test %al,(%rax) RSP: 002b:00007fff4638afa0 EFLAGS: 00000202 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f2b23041186 RDX: 0000000000000010 RSI: 0000557a15fd7360 RDI: 0000000000000003 RBP: 00007fff4638afb0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000106 R13: 000000000000000a R14: 00007f2b2328a000 R15: 0000557a15fd7330 @Greg: Is it possible to drop this patch for the moment? (This patch was probably coming with dependences.) @Ruohan: do you mind looking at this please? I didn't execute TCP specific tests, only MPTCP ones. See: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/23479015653/job/68317986391 Cheers, Matt -- Sponsored by the NGI0 Core fund.