REDHAT-BUG-2418892: Medium severity linux-kernel vulnerability

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

devlink: rate: Unset parent pointer in devlratenodesdestroy

The function devlratenodesdestroy is documented to "Unset parent for all rate objects". However, it was only calling the driver-specific rateleafparentset or ratenodeparentset ops and decrementing the parent's refcount, without actually setting the devlinkrate->parent pointer to NULL.

This leaves a dangling pointer in the devlinkrate struct, which cause refcount error in netdevsim[1] and mlx5[2]. In addition, this is inconsistent with the behavior of devlinknlrateparentnodeset, where the parent pointer is correctly cleared.

This patch fixes the issue by explicitly setting devlinkrate->parent to NULL after notifying the driver, thus fulfilling the function's documented behavior for all rate objects.

[1] repro steps: echo 1 > /sys/bus/netdevsim/newdevice devlink dev eswitch set netdevsim/netdevsim1 mode switchdev echo 1 > /sys/bus/netdevsim/devices/netdevsim1/sriovnumvfs devlink port function rate add netdevsim/netdevsim1/testnode devlink port function rate set netdevsim/netdevsim1/128 parent testnode echo 1 > /sys/bus/netdevsim/deldevice

dmesg: refcountt: decrement hit 0; leaking memory. WARNING: CPU: 8 PID: 1530 at lib/refcount.c:31 refcountwarnsaturate+0x42/0xe0 CPU: 8 UID: 0 PID: 1530 Comm: bash Not tainted 6.18.0-rc4+ #1 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:refcountwarnsaturate+0x42/0xe0 Call Trace: <TASK> devlrateleafdestroy+0x8d/0x90 nsimdevportdel+0x6c/0x70 [netdevsim] nsimdevreloaddestroy+0x11c/0x140 [netdevsim] nsimdrvremove+0x2b/0xb0 [netdevsim] devicereleasedriverinternal+0x194/0x1f0 busremovedevice+0xc6/0x130 devicedel+0x159/0x3c0 deviceunregister+0x1a/0x60 deldevicestore+0x111/0x170 [netdevsim] kernfsfopwriteiter+0x12e/0x1e0 vfswrite+0x215/0x3d0 ksyswrite+0x5f/0xd0 dosyscall64+0x55/0x10f0 entrySYSCALL64afterhwframe+0x4b/0x53

[2] devlink dev eswitch set pci/0000:08:00.0 mode switchdev devlink port add pci/0000:08:00.0 flavour pcisf pfnum 0 sfnum 1000 devlink port function rate add pci/0000:08:00.0/group1 devlink port function rate set pci/0000:08:00.0/32768 parent group1 modprobe -r mlx5ib mlx5fwctl mlx5core

dmesg: refcountt: decrement hit 0; leaking memory. WARNING: CPU: 7 PID: 16151 at lib/refcount.c:31 refcountwarnsaturate+0x42/0xe0 CPU: 7 UID: 0 PID: 16151 Comm: bash Not tainted 6.17.0-rc7forupstreammindebug202510021244 #1 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 RIP: 0010:refcountwarnsaturate+0x42/0xe0 Call Trace: <TASK> devlrateleafdestroy+0x8d/0x90 mlx5eswoffloadsdevlinkportunregister+0x33/0x60 [mlx5core] mlx5eswoffloadsunloadrep+0x3f/0x50 [mlx5core] mlx5eswitchunloadsfvport+0x40/0x90 [mlx5core] mlx5sfeswevent+0xc4/0x120 [mlx5core] notifiercallchain+0x33/0xa0 blockingnotifiercallchain+0x3b/0x50 mlx5eswitchdisablelocked+0x50/0x110 [mlx5core] mlx5eswitchdisable+0x63/0x90 [mlx5core] mlx5unload+0x1d/0x170 [mlx5core] mlx5uninitone+0xa2/0x130 [mlx5core] removeone+0x78/0xd0 [mlx5core] pcideviceremove+0x39/0xa0 devicereleasedriverinternal+0x194/0x1f0 unbindstore+0x99/0xa0 kernfsfopwriteiter+0x12e/0x1e0 vfswrite+0x215/0x3d0 ksyswrite+0x5f/0xd0 dosyscall64+0x53/0x1f0 entrySYSCALL64afterhwframe+0x4b/0x53