cve/published/2025/CVE-2025-21875.mbox - pub/scm/linux/security/vulns - Git at Google

 From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
 From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 To: <linux-cve-announce@vger.kernel.org>
 Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
 Subject: CVE-2025-21875: mptcp: always handle address removal under msk socket lock

 Description
 ===========

 In the Linux kernel, the following vulnerability has been resolved:

 mptcp: always handle address removal under msk socket lock

 Syzkaller reported a lockdep splat in the PM control path:

   WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 sock_owned_by_me include/net/sock.h:1711 [inline]
   WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 msk_owned_by_me net/mptcp/protocol.h:363 [inline]
   WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788
   Modules linked in:
   CPU: 0 UID: 0 PID: 6693 Comm: syz.0.205 Not tainted 6.14.0-rc2-syzkaller-00303-gad1b832bf1cf #0
   Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
   RIP: 0010:sock_owned_by_me include/net/sock.h:1711 [inline]
   RIP: 0010:msk_owned_by_me net/mptcp/protocol.h:363 [inline]
   RIP: 0010:mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788
   Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 ca 7b d3 f5 eb b9 e8 c3 7b d3 f5 90 0f 0b 90 e9 dd fb ff ff e8 b5 7b d3 f5 90 <0f> 0b 90 e9 3e fb ff ff 44 89 f1 80 e1 07 38 c1 0f 8c eb fb ff ff
   RSP: 0000:ffffc900034f6f60 EFLAGS: 00010283
   RAX: ffffffff8bee3c2b RBX: 0000000000000001 RCX: 0000000000080000
   RDX: ffffc90004d42000 RSI: 000000000000a407 RDI: 000000000000a408
   RBP: ffffc900034f7030 R08: ffffffff8bee37f6 R09: 0100000000000000
   R10: dffffc0000000000 R11: ffffed100bcc62e4 R12: ffff88805e6316e0
   R13: ffff88805e630c00 R14: dffffc0000000000 R15: ffff88805e630c00
   FS:  00007f7e9a7e96c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
   CR2: 0000001b2fd18ff8 CR3: 0000000032c24000 CR4: 00000000003526f0
   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
   Call Trace:
    <TASK>
    mptcp_pm_remove_addr+0x103/0x1d0 net/mptcp/pm.c:59
    mptcp_pm_remove_anno_addr+0x1f4/0x2f0 net/mptcp/pm_netlink.c:1486
    mptcp_nl_remove_subflow_and_signal_addr net/mptcp/pm_netlink.c:1518 [inline]
    mptcp_pm_nl_del_addr_doit+0x118d/0x1af0 net/mptcp/pm_netlink.c:1629
    genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
    genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
    genl_rcv_msg+0xb1f/0xec0 net/netlink/genetlink.c:1210
    netlink_rcv_skb+0x206/0x480 net/netlink/af_netlink.c:2543
    genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
    netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
    netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1348
    netlink_sendmsg+0x8de/0xcb0 net/netlink/af_netlink.c:1892
    sock_sendmsg_nosec net/socket.c:718 [inline]
    __sock_sendmsg+0x221/0x270 net/socket.c:733
    ____sys_sendmsg+0x53a/0x860 net/socket.c:2573
    ___sys_sendmsg net/socket.c:2627 [inline]
    __sys_sendmsg+0x269/0x350 net/socket.c:2659
    do_syscall_x64 arch/x86/entry/common.c:52 [inline]
    do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
    entry_SYSCALL_64_after_hwframe+0x77/0x7f
   RIP: 0033:0x7f7e9998cde9
   Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
   RSP: 002b:00007f7e9a7e9038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
   RAX: ffffffffffffffda RBX: 00007f7e99ba5fa0 RCX: 00007f7e9998cde9
   RDX: 000000002000c094 RSI: 0000400000000000 RDI: 0000000000000007
   RBP: 00007f7e99a0e2a0 R08: 0000000000000000 R09: 0000000000000000
   R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
   R13: 0000000000000000 R14: 00007f7e99ba5fa0 R15: 00007fff49231088

 Indeed the PM can try to send a RM_ADDR over a msk without acquiring
 first the msk socket lock.

 The bugged code-path comes from an early optimization: when there
 are no subflows, the PM should (usually) not send RM_ADDR
 notifications.

 The above statement is incorrect, as without locks another process
 could concurrent create a new subflow and cause the RM_ADDR generation.

 Additionally the supposed optimization is not very effective even
 performance-wise, as most mptcp sockets should have at least one
 subflow: the MPC one.

 Address the issue removing the buggy code path, the existing "slow-path"
 will handle correctly even the edge case.

 The Linux kernel CVE team has assigned CVE-2025-21875 to this issue.


 Affected and fixed versions
 ===========================

 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 5.10.235 with commit 494ec285535632732eaa5786297a9ae4f731b5ff
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 5.15.179 with commit 7cca31035c05819643ffb5d7518e9a331b3f6651
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.1.130 with commit 8116fb4acd5d3f06cd37f84887dbe962b6703b1c
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.6.81 with commit a05da2be18aae7e82572f8d795f41bb49f5dfc7d
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.12.18 with commit 4124b782ec2b1e2e490cf0bbf10f53dfd3479890
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.13.6 with commit 2c3de6dff4373f1036e003f49a32629359530bdb
 	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.14 with commit f865c24bc55158313d5779fc81116023a6940ca3

 Please see https://www.kernel.org for a full list of currently supported
 kernel versions by the kernel community.

 Unaffected versions might change over time as fixes are backported to
 older supported kernel versions.  The official CVE entry at
 	https://cve.org/CVERecord/?id=CVE-2025-21875
 will be updated if fixes are backported, please check that for the most
 up to date information about this issue.


 Affected files
 ==============

 The file(s) affected by this issue are:
 	net/mptcp/pm_netlink.c


 Mitigation
 ==========

 The Linux kernel CVE team recommends that you update to the latest
 stable kernel version for this, and many other bugfixes.  Individual
 changes are never tested alone, but rather are part of a larger kernel
 release.  Cherry-picking individual commits is not recommended or
 supported by the Linux kernel community at all.  If however, updating to
 the latest release is impossible, the individual changes to resolve this
 issue can be found at these commits:
 	https://git.kernel.org/stable/c/494ec285535632732eaa5786297a9ae4f731b5ff
 	https://git.kernel.org/stable/c/7cca31035c05819643ffb5d7518e9a331b3f6651
 	https://git.kernel.org/stable/c/8116fb4acd5d3f06cd37f84887dbe962b6703b1c
 	https://git.kernel.org/stable/c/a05da2be18aae7e82572f8d795f41bb49f5dfc7d
 	https://git.kernel.org/stable/c/4124b782ec2b1e2e490cf0bbf10f53dfd3479890
 	https://git.kernel.org/stable/c/2c3de6dff4373f1036e003f49a32629359530bdb
 	https://git.kernel.org/stable/c/f865c24bc55158313d5779fc81116023a6940ca3
	From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
	From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
	To: <linux-cve-announce@vger.kernel.org>
	Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
	Subject: CVE-2025-21875: mptcp: always handle address removal under msk socket lock

	Description
	===========

	In the Linux kernel, the following vulnerability has been resolved:

	mptcp: always handle address removal under msk socket lock

	Syzkaller reported a lockdep splat in the PM control path:

	WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 sock_owned_by_me include/net/sock.h:1711 [inline]
	WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 msk_owned_by_me net/mptcp/protocol.h:363 [inline]
	WARNING: CPU: 0 PID: 6693 at ./include/net/sock.h:1711 mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788
	Modules linked in:
	CPU: 0 UID: 0 PID: 6693 Comm: syz.0.205 Not tainted 6.14.0-rc2-syzkaller-00303-gad1b832bf1cf #0
	Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
	RIP: 0010:sock_owned_by_me include/net/sock.h:1711 [inline]
	RIP: 0010:msk_owned_by_me net/mptcp/protocol.h:363 [inline]
	RIP: 0010:mptcp_pm_nl_addr_send_ack+0x57c/0x610 net/mptcp/pm_netlink.c:788
	Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc e8 ca 7b d3 f5 eb b9 e8 c3 7b d3 f5 90 0f 0b 90 e9 dd fb ff ff e8 b5 7b d3 f5 90 <0f> 0b 90 e9 3e fb ff ff 44 89 f1 80 e1 07 38 c1 0f 8c eb fb ff ff
	RSP: 0000:ffffc900034f6f60 EFLAGS: 00010283
	RAX: ffffffff8bee3c2b RBX: 0000000000000001 RCX: 0000000000080000
	RDX: ffffc90004d42000 RSI: 000000000000a407 RDI: 000000000000a408
	RBP: ffffc900034f7030 R08: ffffffff8bee37f6 R09: 0100000000000000
	R10: dffffc0000000000 R11: ffffed100bcc62e4 R12: ffff88805e6316e0
	R13: ffff88805e630c00 R14: dffffc0000000000 R15: ffff88805e630c00
	FS: 00007f7e9a7e96c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
	CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	CR2: 0000001b2fd18ff8 CR3: 0000000032c24000 CR4: 00000000003526f0
	DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
	DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
	Call Trace:
	<TASK>
	mptcp_pm_remove_addr+0x103/0x1d0 net/mptcp/pm.c:59
	mptcp_pm_remove_anno_addr+0x1f4/0x2f0 net/mptcp/pm_netlink.c:1486
	mptcp_nl_remove_subflow_and_signal_addr net/mptcp/pm_netlink.c:1518 [inline]
	mptcp_pm_nl_del_addr_doit+0x118d/0x1af0 net/mptcp/pm_netlink.c:1629
	genl_family_rcv_msg_doit net/netlink/genetlink.c:1115 [inline]
	genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
	genl_rcv_msg+0xb1f/0xec0 net/netlink/genetlink.c:1210
	netlink_rcv_skb+0x206/0x480 net/netlink/af_netlink.c:2543
	genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
	netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
	netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1348
	netlink_sendmsg+0x8de/0xcb0 net/netlink/af_netlink.c:1892
	sock_sendmsg_nosec net/socket.c:718 [inline]
	__sock_sendmsg+0x221/0x270 net/socket.c:733
	____sys_sendmsg+0x53a/0x860 net/socket.c:2573
	___sys_sendmsg net/socket.c:2627 [inline]
	__sys_sendmsg+0x269/0x350 net/socket.c:2659
	do_syscall_x64 arch/x86/entry/common.c:52 [inline]
	do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
	entry_SYSCALL_64_after_hwframe+0x77/0x7f
	RIP: 0033:0x7f7e9998cde9
	Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
	RSP: 002b:00007f7e9a7e9038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
	RAX: ffffffffffffffda RBX: 00007f7e99ba5fa0 RCX: 00007f7e9998cde9
	RDX: 000000002000c094 RSI: 0000400000000000 RDI: 0000000000000007
	RBP: 00007f7e99a0e2a0 R08: 0000000000000000 R09: 0000000000000000
	R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
	R13: 0000000000000000 R14: 00007f7e99ba5fa0 R15: 00007fff49231088

	Indeed the PM can try to send a RM_ADDR over a msk without acquiring
	first the msk socket lock.

	The bugged code-path comes from an early optimization: when there
	are no subflows, the PM should (usually) not send RM_ADDR
	notifications.

	The above statement is incorrect, as without locks another process
	could concurrent create a new subflow and cause the RM_ADDR generation.

	Additionally the supposed optimization is not very effective even
	performance-wise, as most mptcp sockets should have at least one
	subflow: the MPC one.

	Address the issue removing the buggy code path, the existing "slow-path"
	will handle correctly even the edge case.

	The Linux kernel CVE team has assigned CVE-2025-21875 to this issue.


	Affected and fixed versions
	===========================

	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 5.10.235 with commit 494ec285535632732eaa5786297a9ae4f731b5ff
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 5.15.179 with commit 7cca31035c05819643ffb5d7518e9a331b3f6651
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.1.130 with commit 8116fb4acd5d3f06cd37f84887dbe962b6703b1c
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.6.81 with commit a05da2be18aae7e82572f8d795f41bb49f5dfc7d
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.12.18 with commit 4124b782ec2b1e2e490cf0bbf10f53dfd3479890
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.13.6 with commit 2c3de6dff4373f1036e003f49a32629359530bdb
	Issue introduced in 5.10 with commit b6c08380860b926752d57c8fa9911fa388c4b876 and fixed in 6.14 with commit f865c24bc55158313d5779fc81116023a6940ca3

	Please see https://www.kernel.org for a full list of currently supported
	kernel versions by the kernel community.

	Unaffected versions might change over time as fixes are backported to
	older supported kernel versions. The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21875
	will be updated if fixes are backported, please check that for the most
	up to date information about this issue.


	Affected files
	==============

	The file(s) affected by this issue are:
	net/mptcp/pm_netlink.c


	Mitigation
	==========

	The Linux kernel CVE team recommends that you update to the latest
	stable kernel version for this, and many other bugfixes. Individual
	changes are never tested alone, but rather are part of a larger kernel
	release. Cherry-picking individual commits is not recommended or
	supported by the Linux kernel community at all. If however, updating to
	the latest release is impossible, the individual changes to resolve this
	issue can be found at these commits:
	https://git.kernel.org/stable/c/494ec285535632732eaa5786297a9ae4f731b5ff
	https://git.kernel.org/stable/c/7cca31035c05819643ffb5d7518e9a331b3f6651
	https://git.kernel.org/stable/c/8116fb4acd5d3f06cd37f84887dbe962b6703b1c
	https://git.kernel.org/stable/c/a05da2be18aae7e82572f8d795f41bb49f5dfc7d
	https://git.kernel.org/stable/c/4124b782ec2b1e2e490cf0bbf10f53dfd3479890
	https://git.kernel.org/stable/c/2c3de6dff4373f1036e003f49a32629359530bdb
	https://git.kernel.org/stable/c/f865c24bc55158313d5779fc81116023a6940ca3