CVE-2024-53047

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

mptcp: init: protect sched with rcu_read_lock

Enabling CONFIG_PROVE_RCU_LIST with its dependence CONFIG_RCU_EXPERT creates this splat when an MPTCP socket is created:

============================= WARNING: suspicious RCU usage 6.12.0-rc2+ #11 Not tainted

net/mptcp/sched.c:44 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1 no locks held by mptcp_connect/176.

stack backtrace: CPU: 0 UID: 0 PID: 176 Comm: mptcp_connect Not tainted 6.12.0-rc2+ #11 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:123) lockdep_rcu_suspicious (kernel/locking/lockdep.c:6822) mptcp_sched_find (net/mptcp/sched.c:44 (discriminator 7)) mptcp_init_sock (net/mptcp/protocol.c:2867 (discriminator 1)) ? sock_init_data_uid (arch/x86/include/asm/atomic.h:28) inet_create.part.0.constprop.0 (net/ipv4/af_inet.c:386) ? __sock_create (include/linux/rcupdate.h:347 (discriminator 1)) __sock_create (net/socket.c:1576) __sys_socket (net/socket.c:1671) ? __pfx___sys_socket (net/socket.c:1712) ? do_user_addr_fault (arch/x86/mm/fault.c:1419 (discriminator 1)) __x64_sys_socket (net/socket.c:1728) do_syscall_64 (arch/x86/entry/common.c:52 (discriminator 1)) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

That's because when the socket is initialised, rcu_read_lock() is not used despite the explicit comment written above the declaration of mptcp_sched_find() in sched.c. Adding the missing lock/unlock avoids the warning.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.