vxlan: Annotate FDB data races
The 'used' and 'updated' fields in the FDB entry structure can be
accessed concurrently by multiple threads, leading to reports such as
[1]. Can be reproduced using [2].
Suppress these reports by annotating these accesses using
READ_ONCE() / WRITE_ONCE().
[1]
BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit
write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0:
vxlan_xmit+0xb29/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2:
vxlan_xmit+0xadf/0x2380
dev_hard_start_xmit+0x84/0x2f0
__dev_queue_xmit+0x45a/0x1650
packet_xmit+0x100/0x150
packet_sendmsg+0x2114/0x2ac0
__sys_sendto+0x318/0x330
__x64_sys_sendto+0x76/0x90
x64_sys_call+0x14e8/0x1c00
do_syscall_64+0x9e/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f
Reported by Kernel Concurrency Sanitizer on:
CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
[2]
#!/bin/bash
set +H
echo whitelist > /sys/kernel/debug/kcsan
echo !vxlan_xmit > /sys/kernel/debug/kcsan
ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1
bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1
taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q &
Metrics
Affected Vendors & Products
| Source | ID | Title |
|---|---|---|
Debian DLA |
DLA-4327-1 | linux security update |
Debian DLA |
DLA-4328-1 | linux-6.1 security update |
Debian DSA |
DSA-5973-1 | linux security update |
EUVD |
EUVD-2025-18615 | In the Linux kernel, the following vulnerability has been resolved: vxlan: Annotate FDB data races The 'used' and 'updated' fields in the FDB entry structure can be accessed concurrently by multiple threads, leading to reports such as [1]. Can be reproduced using [2]. Suppress these reports by annotating these accesses using READ_ONCE() / WRITE_ONCE(). [1] BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0: vxlan_xmit+0xb29/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2: vxlan_xmit+0xadf/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f Reported by Kernel Concurrency Sanitizer on: CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 [2] #!/bin/bash set +H echo whitelist > /sys/kernel/debug/kcsan echo !vxlan_xmit > /sys/kernel/debug/kcsan ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1 bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1 taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q & taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q & |
Ubuntu USN |
USN-7704-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7704-2 | Linux kernel (FIPS) vulnerabilities |
Ubuntu USN |
USN-7704-3 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7704-4 | Linux kernel (NVIDIA) vulnerabilities |
Ubuntu USN |
USN-7704-5 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7711-1 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-7712-1 | Linux kernel (Azure FIPS) vulnerabilities |
Ubuntu USN |
USN-7712-2 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-7769-1 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7769-2 | Linux kernel (Real-time) vulnerabilities |
Ubuntu USN |
USN-7769-3 | Linux kernel vulnerabilities |
Ubuntu USN |
USN-7770-1 | Linux kernel (Azure) vulnerabilities |
Ubuntu USN |
USN-7771-1 | Linux kernel (OEM) vulnerabilities |
Ubuntu USN |
USN-7789-1 | Linux kernel (Oracle) vulnerabilities |
Ubuntu USN |
USN-7789-2 | Linux kernel (Raspberry Pi) vulnerabilities |
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
Thu, 18 Dec 2025 21:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Debian
Debian debian Linux |
|
| Weaknesses | NVD-CWE-noinfo | |
| CPEs | cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
|
| Vendors & Products |
Debian
Debian debian Linux |
|
| Metrics |
cvssV3_1
|
cvssV3_1
|
Mon, 03 Nov 2025 18:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
Thu, 26 Jun 2025 02:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
cvssV3_1
|
cvssV3_1
|
Fri, 20 Jun 2025 23:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Wed, 18 Jun 2025 09:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: vxlan: Annotate FDB data races The 'used' and 'updated' fields in the FDB entry structure can be accessed concurrently by multiple threads, leading to reports such as [1]. Can be reproduced using [2]. Suppress these reports by annotating these accesses using READ_ONCE() / WRITE_ONCE(). [1] BUG: KCSAN: data-race in vxlan_xmit / vxlan_xmit write to 0xffff942604d263a8 of 8 bytes by task 286 on cpu 0: vxlan_xmit+0xb29/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff942604d263a8 of 8 bytes by task 287 on cpu 2: vxlan_xmit+0xadf/0x2380 dev_hard_start_xmit+0x84/0x2f0 __dev_queue_xmit+0x45a/0x1650 packet_xmit+0x100/0x150 packet_sendmsg+0x2114/0x2ac0 __sys_sendto+0x318/0x330 __x64_sys_sendto+0x76/0x90 x64_sys_call+0x14e8/0x1c00 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000000fffbac6e -> 0x00000000fffbac6f Reported by Kernel Concurrency Sanitizer on: CPU: 2 UID: 0 PID: 287 Comm: mausezahn Not tainted 6.13.0-rc7-01544-gb4b270f11a02 #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 [2] #!/bin/bash set +H echo whitelist > /sys/kernel/debug/kcsan echo !vxlan_xmit > /sys/kernel/debug/kcsan ip link add name vx0 up type vxlan id 10010 dstport 4789 local 192.0.2.1 bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 198.51.100.1 taskset -c 0 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q & taskset -c 2 mausezahn vx0 -a own -b 00:11:22:33:44:55 -c 0 -q & | |
| Title | vxlan: Annotate FDB data races | |
| References |
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|
Projects
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Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-11-03T17:33:16.449Z
Reserved: 2025-04-16T04:51:23.978Z
Link: CVE-2025-38037
No data.
Status : Analyzed
Published: 2025-06-18T10:15:36.030
Modified: 2025-12-18T21:36:09.150
Link: CVE-2025-38037
OpenCVE Enrichment
Updated: 2025-06-23T09:16:29Z
Debian DLA
Debian DSA
EUVD
Ubuntu USN