igb: clean up in all error paths when enabling SR-IOV

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

igb: clean up in all error paths when enabling SR-IOV

After commit 50f303496d92 ("igb: Enable SR-IOV after reinit"), removing
the igb module could hang or crash (depending on the machine) when the
module has been loaded with the max_vfs parameter set to some value != 0.

In case of one test machine with a dual port 82580, this hang occurred:

[ 232.480687] igb 0000:41:00.1: removed PHC on enp65s0f1
[ 233.093257] igb 0000:41:00.1: IOV Disabled
[ 233.329969] pcieport 0000:40:01.0: AER: Multiple Uncorrected (Non-Fatal) err0
[ 233.340302] igb 0000:41:00.0: PCIe Bus Error: severity=Uncorrected (Non-Fata)
[ 233.352248] igb 0000:41:00.0: device [8086:1516] error status/mask=00100000
[ 233.361088] igb 0000:41:00.0: [20] UnsupReq (First)
[ 233.368183] igb 0000:41:00.0: AER: TLP Header: 40000001 0000040f cdbfc00c c
[ 233.376846] igb 0000:41:00.1: PCIe Bus Error: severity=Uncorrected (Non-Fata)
[ 233.388779] igb 0000:41:00.1: device [8086:1516] error status/mask=00100000
[ 233.397629] igb 0000:41:00.1: [20] UnsupReq (First)
[ 233.404736] igb 0000:41:00.1: AER: TLP Header: 40000001 0000040f cdbfc00c c
[ 233.538214] pci 0000:41:00.1: AER: can't recover (no error_detected callback)
[ 233.538401] igb 0000:41:00.0: removed PHC on enp65s0f0
[ 233.546197] pcieport 0000:40:01.0: AER: device recovery failed
[ 234.157244] igb 0000:41:00.0: IOV Disabled
[ 371.619705] INFO: task irq/35-aerdrv:257 blocked for more than 122 seconds.
[ 371.627489] Not tainted 6.4.0-dirty #2
[ 371.632257] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this.
[ 371.641000] task:irq/35-aerdrv state:D stack:0 pid:257 ppid:2 f0
[ 371.650330] Call Trace:
[ 371.653061] <TASK>
[ 371.655407] __schedule+0x20e/0x660
[ 371.659313] schedule+0x5a/0xd0
[ 371.662824] schedule_preempt_disabled+0x11/0x20
[ 371.667983] __mutex_lock.constprop.0+0x372/0x6c0
[ 371.673237] ? __pfx_aer_root_reset+0x10/0x10
[ 371.678105] report_error_detected+0x25/0x1c0
[ 371.682974] ? __pfx_report_normal_detected+0x10/0x10
[ 371.688618] pci_walk_bus+0x72/0x90
[ 371.692519] pcie_do_recovery+0xb2/0x330
[ 371.696899] aer_process_err_devices+0x117/0x170
[ 371.702055] aer_isr+0x1c0/0x1e0
[ 371.705661] ? __set_cpus_allowed_ptr+0x54/0xa0
[ 371.710723] ? __pfx_irq_thread_fn+0x10/0x10
[ 371.715496] irq_thread_fn+0x20/0x60
[ 371.719491] irq_thread+0xe6/0x1b0
[ 371.723291] ? __pfx_irq_thread_dtor+0x10/0x10
[ 371.728255] ? __pfx_irq_thread+0x10/0x10
[ 371.732731] kthread+0xe2/0x110
[ 371.736243] ? __pfx_kthread+0x10/0x10
[ 371.740430] ret_from_fork+0x2c/0x50
[ 371.744428] </TASK>

The reproducer was a simple script:

#!/bin/sh
for i in `seq 1 5`; do
modprobe -rv igb
modprobe -v igb max_vfs=1
sleep 1
modprobe -rv igb
done

It turned out that this could only be reproduce on 82580 (quad and
dual-port), but not on 82576, i350 and i210. Further debugging showed
that igb_enable_sriov()'s call to pci_enable_sriov() is failing, because
dev->is_physfn is 0 on 82580.

Prior to commit 50f303496d92 ("igb: Enable SR-IOV after reinit"),
igb_enable_sriov() jumped into the "err_out" cleanup branch. After this
commit it only returned the error code.

So the cleanup didn't take place, and the incorrect VF setup in the
igb_adapter structure fooled the igb driver into assuming that VFs have
been set up where no VF actually existed.

Fix this problem by cleaning up again if pci_enable_sriov() fails.