In the Linux kernel, the following vulnerability has been resolved:
Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV"
This reverts commit 05703271c3cd ("PCI/IOV: Add PCI rescan-remove locking
when enabling/disabling SR-IOV"), which causes a deadlock by recursively
taking pci_rescan_remove_lock when sriov_del_vfs() is called as part of
pci_stop_and_remove_bus_device(). For example with the following sequence
of commands:
$ echo <NUM> > /sys/bus/pci/devices/<pf>/sriov_numvfs
$ echo 1 > /sys/bus/pci/devices/<pf>/remove
A trimmed trace of the deadlock on a mlx5 device is as below:
zsh/5715 is trying to acquire lock:
000002597926ef50 (pci_rescan_remove_lock){+.+.}-{3:3}, at: sriov_disable+0x34/0x140
but task is already holding lock:
000002597926ef50 (pci_rescan_remove_lock){+.+.}-{3:3}, at: pci_stop_and_remove_bus_device_locked+0x24/0x80
...
Call Trace:
[<00000259778c4f90>] dump_stack_lvl+0xc0/0x110
[<00000259779c844e>] print_deadlock_bug+0x31e/0x330
[<00000259779c1908>] __lock_acquire+0x16c8/0x32f0
[<00000259779bffac>] lock_acquire+0x14c/0x350
[<00000259789643a6>] __mutex_lock_common+0xe6/0x1520
[<000002597896413c>] mutex_lock_nested+0x3c/0x50
[<00000259784a07e4>] sriov_disable+0x34/0x140
[<00000258f7d6dd80>] mlx5_sriov_disable+0x50/0x80 [mlx5_core]
[<00000258f7d5745e>] remove_one+0x5e/0xf0 [mlx5_core]
[<00000259784857fc>] pci_device_remove+0x3c/0xa0
[<000002597851012e>] device_release_driver_internal+0x18e/0x280
[<000002597847ae22>] pci_stop_bus_device+0x82/0xa0
[<000002597847afce>] pci_stop_and_remove_bus_device_locked+0x5e/0x80
[<00000259784972c2>] remove_store+0x72/0x90
[<0000025977e6661a>] kernfs_fop_write_iter+0x15a/0x200
[<0000025977d7241c>] vfs_write+0x24c/0x300
[<0000025977d72696>] ksys_write+0x86/0x110
[<000002597895b61c>] __do_syscall+0x14c/0x400
[<000002597896e0ee>] system_call+0x6e/0x90
This alone is not a complete fix as it restores the issue the cited commit
tried to solve. A new fix will be provided as a follow on.