From fc8c818e756991f5f50b8dfab07f970a18da2556 Mon Sep 17 00:00:00 2001 From: Philipp Stanner Date: Thu, 5 Sep 2024 09:25:57 +0200 Subject: [PATCH] PCI: Fix potential deadlock in pcim_intx() 25216afc9db5 ("PCI: Add managed pcim_intx()") moved the allocation step for pci_intx()'s device resource from pcim_enable_device() to pcim_intx(). As before, pcim_enable_device() sets pci_dev.is_managed to true; and it is never set to false again. Due to the lifecycle of a struct pci_dev, it can happen that a second driver obtains the same pci_dev after a first driver ran. If one driver uses pcim_enable_device() and the other doesn't, this causes the other driver to run into managed pcim_intx(), which will try to allocate when called for the first time. Allocations might sleep, so calling pci_intx() while holding spinlocks becomes then invalid, which causes lockdep warnings and could cause deadlocks: ======================================================== WARNING: possible irq lock inversion dependency detected 6.11.0-rc6+ #59 Tainted: G W -------------------------------------------------------- CPU 0/KVM/1537 just changed the state of lock: ffffa0f0cff965f0 (&vdev->irqlock){-...}-{2:2}, at: vfio_intx_handler+0x21/0xd0 [vfio_pci_core] but this lock took another, HARDIRQ-unsafe lock in the past: (fs_reclaim){+.+.}-{0:0} and interrupts could create inverse lock ordering between them. other info that might help us debug this: Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); local_irq_disable(); lock(&vdev->irqlock); lock(fs_reclaim); lock(&vdev->irqlock); *** DEADLOCK *** Have pcim_enable_device()'s release function, pcim_disable_device(), set pci_dev.is_managed to false so that subsequent drivers using the same struct pci_dev do not implicitly run into managed code. Link: https://lore.kernel.org/r/20240905072556.11375-2-pstanner@redhat.com Fixes: 25216afc9db5 ("PCI: Add managed pcim_intx()") Reported-by: Alex Williamson Closes: https://lore.kernel.org/all/20240903094431.63551744.alex.williamson@redhat.com/ Suggested-by: Alex Williamson Signed-off-by: Philipp Stanner Signed-off-by: Bjorn Helgaas Tested-by: Alex Williamson Reviewed-by: Damien Le Moal --- drivers/pci/devres.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c index 3780a9f9ec003..c7affbbf73ab3 100644 --- a/drivers/pci/devres.c +++ b/drivers/pci/devres.c @@ -483,6 +483,8 @@ static void pcim_disable_device(void *pdev_raw) if (!pdev->pinned) pci_disable_device(pdev); + + pdev->is_managed = false; } /**