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

rxrpc: Fix irq-disabled in local_bh_enable()

The rxrpc_assess_MTU_size() function calls down into the IP layer to find
out the MTU size for a route. When accepting an incoming call, this is
called from rxrpc_new_incoming_call() which holds interrupts disabled
across the code that calls down to it. Unfortunately, the IP layer uses
local_bh_enable() which, config dependent, throws a warning if IRQs are
enabled:

WARNING: CPU: 1 PID: 5544 at kernel/softirq.c:387 __local_bh_enable_ip+0x43/0xd0
...
RIP: 0010:__local_bh_enable_ip+0x43/0xd0
...
Call Trace:
<TASK>
rt_cache_route+0x7e/0xa0
rt_set_nexthop.isra.0+0x3b3/0x3f0
__mkroute_output+0x43a/0x460
ip_route_output_key_hash+0xf7/0x140
ip_route_output_flow+0x1b/0x90
rxrpc_assess_MTU_size.isra.0+0x2a0/0x590
rxrpc_new_incoming_peer+0x46/0x120
rxrpc_alloc_incoming_call+0x1b1/0x400
rxrpc_new_incoming_call+0x1da/0x5e0
rxrpc_input_packet+0x827/0x900
rxrpc_io_thread+0x403/0xb60
kthread+0x2f7/0x310
ret_from_fork+0x2a/0x230
ret_from_fork_asm+0x1a/0x30
...
hardirqs last enabled at (23): _raw_spin_unlock_irq+0x24/0x50
hardirqs last disabled at (24): _raw_read_lock_irq+0x17/0x70
softirqs last enabled at (0): copy_process+0xc61/0x2730
softirqs last disabled at (25): rt_add_uncached_list+0x3c/0x90

Fix this by moving the call to rxrpc_assess_MTU_size() out of
rxrpc_init_peer() and further up the stack where it can be done without
interrupts disabled.

It shouldn't be a problem for rxrpc_new_incoming_call() to do it after the
locks are dropped as pmtud is going to be performed by the I/O thread - and
we're in the I/O thread at this point.
Published: 2025-08-16
Score: 5.5 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
EUVD EUVD EUVD-2025-27884 In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix irq-disabled in local_bh_enable() The rxrpc_assess_MTU_size() function calls down into the IP layer to find out the MTU size for a route. When accepting an incoming call, this is called from rxrpc_new_incoming_call() which holds interrupts disabled across the code that calls down to it. Unfortunately, the IP layer uses local_bh_enable() which, config dependent, throws a warning if IRQs are enabled: WARNING: CPU: 1 PID: 5544 at kernel/softirq.c:387 __local_bh_enable_ip+0x43/0xd0 ... RIP: 0010:__local_bh_enable_ip+0x43/0xd0 ... Call Trace: <TASK> rt_cache_route+0x7e/0xa0 rt_set_nexthop.isra.0+0x3b3/0x3f0 __mkroute_output+0x43a/0x460 ip_route_output_key_hash+0xf7/0x140 ip_route_output_flow+0x1b/0x90 rxrpc_assess_MTU_size.isra.0+0x2a0/0x590 rxrpc_new_incoming_peer+0x46/0x120 rxrpc_alloc_incoming_call+0x1b1/0x400 rxrpc_new_incoming_call+0x1da/0x5e0 rxrpc_input_packet+0x827/0x900 rxrpc_io_thread+0x403/0xb60 kthread+0x2f7/0x310 ret_from_fork+0x2a/0x230 ret_from_fork_asm+0x1a/0x30 ... hardirqs last enabled at (23): _raw_spin_unlock_irq+0x24/0x50 hardirqs last disabled at (24): _raw_read_lock_irq+0x17/0x70 softirqs last enabled at (0): copy_process+0xc61/0x2730 softirqs last disabled at (25): rt_add_uncached_list+0x3c/0x90 Fix this by moving the call to rxrpc_assess_MTU_size() out of rxrpc_init_peer() and further up the stack where it can be done without interrupts disabled. It shouldn't be a problem for rxrpc_new_incoming_call() to do it after the locks are dropped as pmtud is going to be performed by the I/O thread - and we're in the I/O thread at this point.
Ubuntu USN Ubuntu USN USN-7879-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7879-2 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7880-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7879-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7879-4 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7934-1 Linux kernel (Azure) vulnerabilities
History

Tue, 18 Nov 2025 22:00:00 +0000

Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.16:rc6:*:*:*:*:*:*

Sun, 24 Aug 2025 22:30:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Vendors & Products Linux
Linux linux Kernel

Mon, 18 Aug 2025 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Sat, 16 Aug 2025 11:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix irq-disabled in local_bh_enable() The rxrpc_assess_MTU_size() function calls down into the IP layer to find out the MTU size for a route. When accepting an incoming call, this is called from rxrpc_new_incoming_call() which holds interrupts disabled across the code that calls down to it. Unfortunately, the IP layer uses local_bh_enable() which, config dependent, throws a warning if IRQs are enabled: WARNING: CPU: 1 PID: 5544 at kernel/softirq.c:387 __local_bh_enable_ip+0x43/0xd0 ... RIP: 0010:__local_bh_enable_ip+0x43/0xd0 ... Call Trace: <TASK> rt_cache_route+0x7e/0xa0 rt_set_nexthop.isra.0+0x3b3/0x3f0 __mkroute_output+0x43a/0x460 ip_route_output_key_hash+0xf7/0x140 ip_route_output_flow+0x1b/0x90 rxrpc_assess_MTU_size.isra.0+0x2a0/0x590 rxrpc_new_incoming_peer+0x46/0x120 rxrpc_alloc_incoming_call+0x1b1/0x400 rxrpc_new_incoming_call+0x1da/0x5e0 rxrpc_input_packet+0x827/0x900 rxrpc_io_thread+0x403/0xb60 kthread+0x2f7/0x310 ret_from_fork+0x2a/0x230 ret_from_fork_asm+0x1a/0x30 ... hardirqs last enabled at (23): _raw_spin_unlock_irq+0x24/0x50 hardirqs last disabled at (24): _raw_read_lock_irq+0x17/0x70 softirqs last enabled at (0): copy_process+0xc61/0x2730 softirqs last disabled at (25): rt_add_uncached_list+0x3c/0x90 Fix this by moving the call to rxrpc_assess_MTU_size() out of rxrpc_init_peer() and further up the stack where it can be done without interrupts disabled. It shouldn't be a problem for rxrpc_new_incoming_call() to do it after the locks are dropped as pmtud is going to be performed by the I/O thread - and we're in the I/O thread at this point.
Title rxrpc: Fix irq-disabled in local_bh_enable()
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-11T21:29:42.490Z

Reserved: 2025-04-16T04:51:24.023Z

Link: CVE-2025-38525

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2025-08-16T12:15:27.933

Modified: 2025-11-18T21:58:19.050

Link: CVE-2025-38525

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-08-16T00:00:00Z

Links: CVE-2025-38525 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-08-24T22:19:15Z

Weaknesses