CVE-2025-21938

/// Technical description

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

mptcp: fix 'scheduling while atomic' in mptcp_pm_nl_append_new_local_addr

If multiple connection requests attempt to create an implicit mptcp

endpoint in parallel, more than one caller may end up in

mptcp_pm_nl_append_new_local_addr because none found the address in

local_addr_list during their call to mptcp_pm_nl_get_local_id. In this

case, the concurrent new_local_addr calls may delete the address entry

created by the previous caller. These deletes use synchronize_rcu, but

this is not permitted in some of the contexts where this function may be

called. During packet recv, the caller may be in a rcu read critical

section and have preemption disabled.

An example stack:

BUG: scheduling while atomic: swapper/2/0/0x00000302

Call Trace:

<IRQ>

dump_stack_lvl (lib/dump_stack.c:117 (discriminator 1))

dump_stack (lib/dump_stack.c:124)

__schedule_bug (kernel/sched/core.c:5943)

schedule_debug.constpr

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References