[SRU][J][PATCH 0/1] CVE-2025-21801

[Cengiz Can]

https://ubuntu.com/security/CVE-2025-21801

[ Impact ]

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

net: ravb: Fix missing rtnl lock in suspend/resume path

Fix the suspend/resume path by ensuring the rtnl lock is held where required.
Calls to ravb_open, ravb_close and wol operations must be performed under the
rtnl lock to prevent conflicts with ongoing ndo operations.

Without this fix, the following warning is triggered: [ 39.032969]
============================= [ 39.032983] WARNING: suspicious RCU usage [
39.033019] ----------------------------- [ 39.033033]
drivers/net/phy/phy_device.c:2004 suspicious rcu_dereference_protected() usage!
... [ 39.033597] stack backtrace: [ 39.033613] CPU: 0 UID: 0 PID: 174 Comm:
python3 Not tainted 6.13.0-rc7-next-20250116-arm64-renesas-00002-g35245dfdc62c
#7 [ 39.033623] Hardware name: Renesas SMARC EVK version 2 based on
r9a08g045s33 (DT) [ 39.033628] Call trace: [ 39.033633] show_stack+0x14/0x1c
(C) [ 39.033652] dump_stack_lvl+0xb4/0xc4 [ 39.033664] dump_stack+0x14/0x1c [
39.033671] lockdep_rcu_suspicious+0x16c/0x22c [ 39.033682]
phy_detach+0x160/0x190 [ 39.033694] phy_disconnect+0x40/0x54 [ 39.033703]
ravb_close+0x6c/0x1cc [ 39.033714] ravb_suspend+0x48/0x120 [ 39.033721]
dpm_run_callback+0x4c/0x14c [ 39.033731] device_suspend+0x11c/0x4dc [
39.033740] dpm_suspend+0xdc/0x214 [ 39.033748] dpm_suspend_start+0x48/0x60 [
39.033758] suspend_devices_and_enter+0x124/0x574 [ 39.033769]
pm_suspend+0x1ac/0x274 [ 39.033778] state_store+0x88/0x124 [ 39.033788]
kobj_attr_store+0x14/0x24 [ 39.033798] sysfs_kf_write+0x48/0x6c [ 39.033808]
kernfs_fop_write_iter+0x118/0x1a8 [ 39.033817] vfs_write+0x27c/0x378 [
39.033825] ksys_write+0x64/0xf4 [ 39.033833] __arm64_sys_write+0x18/0x20 [
39.033841] invoke_syscall+0x44/0x104 [ 39.033852]
el0_svc_common.constprop.0+0xb4/0xd4 [ 39.033862] do_el0_svc+0x18/0x20 [
39.033870] el0_svc+0x3c/0xf0 [ 39.033880] el0t_64_sync_handler+0xc0/0xc4 [
39.033888] el0t_64_sync+0x154/0x158 [ 39.041274] ravb 11c30000.ethernet eth0:
Link is Down

[ Fix ]

jammy/linux: backported from 2c2ebb2b4957

This tree's ravb_suspend/ravb_resume predate upstream's reset_control and
pm_runtime_force_* rework, so instead of upstream's early-return structure the
backport wraps this tree's actual rtnl-requiring calls under rtnl_lock: the
if/else ravb_wol_setup/ravb_close block in suspend, and the
ravb_wol_restore/ravb_open sequence inside the netif_running block in resume
(unlocking on the error paths). This preserves the WoL/close/open behaviour
while carrying upstream's locking intent.

[ Test Plan ]

Build and boot tested.

[ Where Problems Could Occur ]

A bad fix would primarily affect Renesas SoCs using the ravb (Ethernet AVB)
driver, such as R-Car and RZ/G platforms, during system suspend and resume,
including Wake-on-LAN configuration and network interface open/close on those
paths. An incorrect change to the rtnl locking could deadlock or leave the
lock held on an error path, stalling the network stack during suspend/resume.
Systems without ravb hardware are not affected, and this only exercises code
reached through suspend/resume.

[ Other Info ]

Kybele flow-v11-22-gf3c7ff80. Reference: 6d5481ab/v1