CVE-2025-21663 Affecting kernel-rt-devel package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-devel package and not the kernel-rt-devel package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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

net: stmmac: dwmac-tegra: Read iommu stream id from device tree

Nvidia's Tegra MGBE controllers require the IOMMU "Stream ID" (SID) to be written to the MGBE_WRAP_AXI_ASID0_CTRL register.

The current driver is hard coded to use MGBE0's SID for all controllers. This causes softirq time outs and kernel panics when using controllers other than MGBE0.

Example dmesg errors when an ethernet cable is connected to MGBE1:

[ 116.133290] tegra-mgbe 6910000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx [ 121.851283] tegra-mgbe 6910000.ethernet eth1: NETDEV WATCHDOG: CPU: 5: transmit queue 0 timed out 5690 ms [ 121.851782] tegra-mgbe 6910000.ethernet eth1: Reset adapter. [ 121.892464] tegra-mgbe 6910000.ethernet eth1: Register MEM_TYPE_PAGE_POOL RxQ-0 [ 121.905920] tegra-mgbe 6910000.ethernet eth1: PHY [stmmac-1:00] driver [Aquantia AQR113] (irq=171) [ 121.907356] tegra-mgbe 6910000.ethernet eth1: Enabling Safety Features [ 121.907578] tegra-mgbe 6910000.ethernet eth1: IEEE 1588-2008 Advanced Timestamp supported [ 121.908399] tegra-mgbe 6910000.ethernet eth1: registered PTP clock [ 121.908582] tegra-mgbe 6910000.ethernet eth1: configuring for phy/10gbase-r link mode [ 125.961292] tegra-mgbe 6910000.ethernet eth1: Link is Up - 1Gbps/Full - flow control rx/tx [ 181.921198] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 181.921404] rcu: 7-....: (1 GPs behind) idle=540c/1/0x4000000000000002 softirq=1748/1749 fqs=2337 [ 181.921684] rcu: (detected by 4, t=6002 jiffies, g=1357, q=1254 ncpus=8) [ 181.921878] Sending NMI from CPU 4 to CPUs 7: [ 181.921886] NMI backtrace for cpu 7 [ 181.922131] CPU: 7 UID: 0 PID: 0 Comm: swapper/7 Kdump: loaded Not tainted 6.13.0-rc3+ #6 [ 181.922390] Hardware name: NVIDIA CTI Forge + Orin AGX/Jetson, BIOS 202402.1-Unknown 10/28/2024 [ 181.922658] pstate: 40400009 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 181.922847] pc : handle_softirqs+0x98/0x368 [ 181.922978] lr : __do_softirq+0x18/0x20 [ 181.923095] sp : ffff80008003bf50 [ 181.923189] x29: ffff80008003bf50 x28: 0000000000000008 x27: 0000000000000000 [ 181.923379] x26: ffffce78ea277000 x25: 0000000000000000 x24: 0000001c61befda0 [ 181.924486] x23: 0000000060400009 x22: ffffce78e99918bc x21: ffff80008018bd70 [ 181.925568] x20: ffffce78e8bb00d8 x19: ffff80008018bc20 x18: 0000000000000000 [ 181.926655] x17: ffff318ebe7d3000 x16: ffff800080038000 x15: 0000000000000000 [ 181.931455] x14: ffff000080816680 x13: ffff318ebe7d3000 x12: 000000003464d91d [ 181.938628] x11: 0000000000000040 x10: ffff000080165a70 x9 : ffffce78e8bb0160 [ 181.945804] x8 : ffff8000827b3160 x7 : f9157b241586f343 x6 : eeb6502a01c81c74 [ 181.953068] x5 : a4acfcdd2e8096bb x4 : ffffce78ea277340 x3 : 00000000ffffd1e1 [ 181.960329] x2 : 0000000000000101 x1 : ffffce78ea277340 x0 : ffff318ebe7d3000 [ 181.967591] Call trace: [ 181.970043] handle_softirqs+0x98/0x368 (P) [ 181.974240] __do_softirq+0x18/0x20 [ 181.977743] ____do_softirq+0x14/0x28 [ 181.981415] call_on_irq_stack+0x24/0x30 [ 181.985180] do_softirq_own_stack+0x20/0x30 [ 181.989379] __irq_exit_rcu+0x114/0x140 [ 181.993142] irq_exit_rcu+0x14/0x28 [ 181.996816] el1_interrupt+0x44/0xb8 [ 182.000316] el1h_64_irq_handler+0x14/0x20 [ 182.004343] el1h_64_irq+0x80/0x88 [ 182.007755] cpuidle_enter_state+0xc4/0x4a8 (P) [ 182.012305] cpuidle_enter+0x3c/0x58 [ 182.015980] cpuidle_idle_call+0x128/0x1c0 [ 182.020005] do_idle+0xe0/0xf0 [ 182.023155] cpu_startup_entry+0x3c/0x48 [ 182.026917] secondary_start_kernel+0xdc/0x120 [ 182.031379] __secondary_switched+0x74/0x78 [ 212.971162] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 7-.... } 6103 jiffies s: 417 root: 0x80/. [ 212.985935] rcu: blocking rcu_node structures (internal RCU debug): [ 212.992758] Sending NMI from CPU 0 to CPUs 7: [ 212.998539] NMI backtrace for cpu 7 [ 213.004304] CPU: 7 UID: 0 PI ---truncated---

• https://access.redhat.com/security/cve/CVE-2025-21663
• https://git.kernel.org/stable/c/235419f0956e8c60e597aa1619ded8bda7460bb4
• https://git.kernel.org/stable/c/426046e2d62dd19533808661e912b8e8a9eaec16
• https://git.kernel.org/stable/c/b04d33cdbc958a3fd57f3544d4f78b99d9d11909