CVE: CVE-2025-39831
Published: 2025-09-16
Description: In the Linux kernel, the following vulnerability has been resolved:

fbnic: Move phylink resume out of service_task and into open/close

The fbnic driver was presenting with the following locking assert coming
out of a PM resume:
[   42.208116][  T164] RTNL: assertion failed at drivers/net/phy/phylink.c (2611)
[   42.208492][  T164] WARNING: CPU: 1 PID: 164 at drivers/net/phy/phylink.c:2611 phylink_resume+0x190/0x1e0
[   42.208872][  T164] Modules linked in:
[   42.209140][  T164] CPU: 1 UID: 0 PID: 164 Comm: bash Not tainted 6.17.0-rc2-virtme #134 PREEMPT(full)
[   42.209496][  T164] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-5.fc42 04/01/2014
[   42.209861][  T164] RIP: 0010:phylink_resume+0x190/0x1e0
[   42.210057][  T164] Code: 83 e5 01 0f 85 b0 fe ff ff c6 05 1c cd 3e 02 01 90 ba 33 0a 00 00 48 c7 c6 20 3a 1d a5 48 c7 c7 e0 3e 1d a5 e8 21 b8 90 fe 90 <0f> 0b 90 90 e9 86 fe ff ff e8 42 ea 1f ff e9 e2 fe ff ff 48 89 ef
[   42.210708][  T164] RSP: 0018:ffffc90000affbd8 EFLAGS: 00010296
[   42.210983][  T164] RAX: [PII_REDACTED] RBX: ffff8880078d8400 RCX: [PII_REDACTED]
[   42.211235][  T164] RDX: [PII_REDACTED] RSI: 1ffffffff4f10938 RDI: [PII_REDACTED]
[   42.211466][  T164] RBP: [PII_REDACTED] R08: ffffffffa2ae79ea R09: fffffbfff4b3eb84
[   42.211707][  T164] R10: [PII_REDACTED] R11: [PII_REDACTED] R12: ffff888007ad8000
[   42.211997][  T164] R13: [PII_REDACTED] R14: ffff888006a18800 R15: ffffffffa34c59e0
[   42.212234][  T164] FS:  00007f0dc8e39740(0000) GS:ffff88808f51f000(0000) knlGS:[PII_REDACTED]
[   42.212505][  T164] CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
[   42.212704][  T164] CR2: 00007f0dc8e9fe10 CR3: 000000000b56d003 CR4:[PII_REDACTED]772ef0
[   42.213227][  T164] PKRU: 55555554
[   42.213366][  T164] Call Trace:
[   42.213483][  T164]  <TASK>
[   42.213565][  T164]  __fbnic_pm_attach.isra.0+0x8e/0xa0
[   42.213725][  T164]  pci_reset_function+0x116/0x1d0
[   42.213895][  T164]  reset_store+0xa0/0x100
[   42.214025][  T164]  ? pci_dev_reset_attr_is_visible+0x50/0x50
[   42.214221][  T164]  ? sysfs_file_kobj+0xc1/0x1e0
[   42.214374][  T164]  ? sysfs_kf_write+0x65/0x160
[   42.214526][  T164]  kernfs_fop_write_iter+0x2f8/0x4c0
[   42.214677][  T164]  ? kernfs_vma_page_mkwrite+0x1f0/0x1f0
[   42.214836][  T164]  new_sync_write+0x308/0x6f0
[   42.214987][  T164]  ? __lock_acquire+0x34c/0x740
[   42.215135][  T164]  ? new_sync_read+0x6f0/0x6f0
[   42.215288][  T164]  ? lock_acquire.part.0+0xbc/0x260
[   42.215440][  T164]  ? ksys_write+0xff/0x200
[   42.215590][  T164]  ? perf_trace_sched_switch+0x6d0/0x6d0
[   42.215742][  T164]  vfs_write+0x65e/0xbb0
[   42.215876][  T164]  ksys_write+0xff/0x200
[   42.215994][  T164]  ? __ia32_sys_read+0xc0/0xc0
[   42.216141][  T164]  ? do_user_addr_fault+0x269/0x9f0
[   42.216292][  T164]  ? rcu_is_watching+0x15/0xd0
[   42.216442][  T164]  do_syscall_64+0xbb/0x360
[   42.216591][  T164]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[   42.216784][  T164] RIP: 0033:0x7f0dc8ea9986

A bit of digging showed that we were invoking the phylink_resume as a part
of the fbnic_up path when we were enabling the service task while not
holding the RTNL lock. We should be enabling this sooner as a part of the
ndo_open path and then just letting the service task come online later.
This will help to enforce the correct locking and brings the phylink
interface online at the same time as the network interface, instead of at a
later time.

I tested this on QEMU to verify this was working by putting the system to
sleep using "echo mem > /sys/power/state" to put the system to sleep in the
guest and then using the command "system_wakeup" in the QEMU monitor.
CVSS Score: 5.5 (MEDIUM)
References: https://git.kernel.org/stable/c/3ac5f54e47eb348a4bc26e600c63b4d778a22e23; https://git.kernel.org/stable/c/6ede14a2c6365e7e5d855643c7c8390b5268c467; https://git.kernel.org/stable/c/7aab65c62a8a8b48c02e600fe9367b2af662fcb6