The driver could possibly sleep while in atomic context resulting in the following call trace while CONFIG_DEBUG_ATOMIC_SLEEP=y is set: BUG: sleeping function called from invalid context at kernel/locking/mutex.c:283 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 2817, name: bash preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 Call Trace: <TASK> dump_stack_lvl+0x36/0x50 __might_resched+0x123/0x170 mutex_lock+0x1e/0x50 pds_vfio_put_lm_file+0x1e/0xa0 [pds_vfio_pci] pds_vfio_put_save_file+0x19/0x30 [pds_vfio_pci] pds_vfio_state_mutex_unlock+0x2e/0x80 [pds_vfio_pci] pci_reset_function+0x4b/0x70 reset_store+0x5b/0xa0 kernfs_fop_write_iter+0x137/0x1d0 vfs_write+0x2de/0x410 ksys_write+0x5d/0xd0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 This can happen if pds_vfio_put_restore_file() and/or pds_vfio_put_save_file() grab the mutex_lock(&lm_file->lock) while the spin_lock(&pds_vfio->reset_lock) is held, which can happen during while calling pds_vfio_state_mutex_unlock(). Fix this by using a local state variable to represent the current vfio device state and update all the next state values. Then release the spin_unlock(&pds_vfio->reset_lock) before checking if the current vfio device state is VFIO_DEVICE_STATE_ERROR. Then calling pds_vfio_put_restore_file() and pds_vfio_put_save_file() are no longer being done while holding the reset_lock. The only possible concerns are other threads that may call pds_vfio_put_restore_file(), pds_vfio_put_save_file(), and/or pds_vfio_dirty_disable(). However, those paths are already protected by the state mutex_lock(), which is held in this context. Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Closes: https://lore.kernel.org/kvm/1f9bc27b-3de9-4891-9687-ba2820c1b390@moroto.mountain/ Signed-off-by: Brett Creeley <brett.creeley@xxxxxxx> Reviewed-by: Shannon Nelson <shannon.nelson@xxxxxxx> --- drivers/vfio/pci/pds/vfio_dev.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/vfio/pci/pds/vfio_dev.c b/drivers/vfio/pci/pds/vfio_dev.c index 306b1c25f016..cf7f639ba0ec 100644 --- a/drivers/vfio/pci/pds/vfio_dev.c +++ b/drivers/vfio/pci/pds/vfio_dev.c @@ -31,15 +31,17 @@ void pds_vfio_state_mutex_unlock(struct pds_vfio_pci_device *pds_vfio) again: spin_lock(&pds_vfio->reset_lock); if (pds_vfio->deferred_reset) { + enum vfio_device_mig_state current_state = pds_vfio->state; + pds_vfio->deferred_reset = false; - if (pds_vfio->state == VFIO_DEVICE_STATE_ERROR) { + pds_vfio->state = pds_vfio->deferred_reset_state; + pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_RUNNING; + spin_unlock(&pds_vfio->reset_lock); + if (current_state == VFIO_DEVICE_STATE_ERROR) { pds_vfio_put_restore_file(pds_vfio); pds_vfio_put_save_file(pds_vfio); pds_vfio_dirty_disable(pds_vfio, false); } - pds_vfio->state = pds_vfio->deferred_reset_state; - pds_vfio->deferred_reset_state = VFIO_DEVICE_STATE_RUNNING; - spin_unlock(&pds_vfio->reset_lock); goto again; } mutex_unlock(&pds_vfio->state_mutex); -- 2.17.1
