| Message ID | 8e4bcd4116fd94f592f2bf2749f168099c480ddf.1718707743.git.lukas@wunner.de (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI/DPC: Fix use-after-free on concurrent DPC and hot-removal | expand |
On Tue, Jun 18, 2024 at 12:54:55PM +0200, Lukas Wunner wrote: > Keith reports a use-after-free when a DPC event occurs concurrently to > hot-removal of the same portion of the hierarchy: > > The dpc_handler() awaits readiness of the secondary bus below the > Downstream Port where the DPC event occurred. To do so, it polls the > config space of the first child device on the secondary bus. If that > child device is concurrently removed, accesses to its struct pci_dev > cause the kernel to oops. > > That's because pci_bridge_wait_for_secondary_bus() neglects to hold a > reference on the child device. Before v6.3, the function was only > called on resume from system sleep or on runtime resume. Holding a > reference wasn't necessary back then because the pciehp IRQ thread > could never run concurrently. (On resume from system sleep, IRQs are > not enabled until after the resume_noirq phase. And runtime resume is > always awaited before a PCI device is removed.) > > However starting with v6.3, pci_bridge_wait_for_secondary_bus() is also > called on a DPC event. Commit 53b54ad074de ("PCI/DPC: Await readiness > of secondary bus after reset"), which introduced that, failed to > appreciate that pci_bridge_wait_for_secondary_bus() now needs to hold a > reference on the child device because dpc_handler() and pciehp may > indeed run concurrently. The commit was backported to v5.10+ stable > kernels, so that's the oldest one affected. > > Add the missing reference acquisition. > > Abridged stack trace: > > BUG: unable to handle page fault for address: 00000000091400c0 > CPU: 15 PID: 2464 Comm: irq/53-pcie-dpc 6.9.0 > RIP: pci_bus_read_config_dword+0x17/0x50 > pci_dev_wait() > pci_bridge_wait_for_secondary_bus() > dpc_reset_link() > pcie_do_recovery() > dpc_handler() > > Fixes: 53b54ad074de ("PCI/DPC: Await readiness of secondary bus after reset") > Reported-by: Keith Busch <kbusch@kernel.org> > Closes: https://lore.kernel.org/r/20240612181625.3604512-3-kbusch@meta.com/ > Tested-by: Keith Busch <kbusch@kernel.org> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Reviewed-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
On Tue, Jun 18, 2024 at 12:54:55PM +0200, Lukas Wunner wrote: > However starting with v6.3, pci_bridge_wait_for_secondary_bus() is also > called on a DPC event. Commit 53b54ad074de ("PCI/DPC: Await readiness > of secondary bus after reset"), which introduced that, failed to > appreciate that pci_bridge_wait_for_secondary_bus() now needs to hold a > reference on the child device because dpc_handler() and pciehp may > indeed run concurrently. The commit was backported to v5.10+ stable > kernels, so that's the oldest one affected. Caution on applying this to 5.10 and 5.15 stable branches: they don't have the fancy "__free" cleanup you're using here. The newer active stables are okay, though. > int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) > { > - struct pci_dev *child; > + struct pci_dev *child __free(pci_dev_put) = NULL; > int delay;
On Tue, Jun 18, 2024 at 10:12:32AM -0600, Keith Busch wrote: > On Tue, Jun 18, 2024 at 12:54:55PM +0200, Lukas Wunner wrote: > > However starting with v6.3, pci_bridge_wait_for_secondary_bus() is also > > called on a DPC event. Commit 53b54ad074de ("PCI/DPC: Await readiness > > of secondary bus after reset"), which introduced that, failed to > > appreciate that pci_bridge_wait_for_secondary_bus() now needs to hold a > > reference on the child device because dpc_handler() and pciehp may > > indeed run concurrently. The commit was backported to v5.10+ stable > > kernels, so that's the oldest one affected. > > Caution on applying this to 5.10 and 5.15 stable branches: they don't > have the fancy "__free" cleanup you're using here. The newer active > stables are okay, though. I'll let Greg & Sasha know when they start applying this to stable kernels that ced085ef369a is a prerequisite for v5.10-stable and v5.15-stable. I can rework the patch if they don't want to apply ced085ef369a to these older versions. Thanks, Lukas
On Tue, Jun 18, 2024 at 12:54:55PM +0200, Lukas Wunner wrote: > Add the missing reference acquisition. > > Abridged stack trace: > > BUG: unable to handle page fault for address: 00000000091400c0 > CPU: 15 PID: 2464 Comm: irq/53-pcie-dpc 6.9.0 > RIP: pci_bus_read_config_dword+0x17/0x50 > pci_dev_wait() > pci_bridge_wait_for_secondary_bus() > dpc_reset_link() > pcie_do_recovery() > dpc_handler() > > Fixes: 53b54ad074de ("PCI/DPC: Await readiness of secondary bus after reset") > Reported-by: Keith Busch <kbusch@kernel.org> > Closes: https://lore.kernel.org/r/20240612181625.3604512-3-kbusch@meta.com/ > Tested-by: Keith Busch <kbusch@kernel.org> > Signed-off-by: Lukas Wunner <lukas@wunner.de> > Reviewed-by: Keith Busch <kbusch@kernel.org> > Cc: stable@vger.kernel.org # v5.10+ Hey, it's been some time, so just wanted to check on this patch status. It's still a good fix.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index d2c388761ba9..0e7cb507a5d6 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4753,7 +4753,7 @@ static int pci_bus_max_d3cold_delay(const struct pci_bus *bus) */ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) { - struct pci_dev *child; + struct pci_dev *child __free(pci_dev_put) = NULL; int delay; if (pci_dev_is_disconnected(dev)) @@ -4782,8 +4782,8 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) return 0; } - child = list_first_entry(&dev->subordinate->devices, struct pci_dev, - bus_list); + child = pci_dev_get(list_first_entry(&dev->subordinate->devices, + struct pci_dev, bus_list)); up_read(&pci_bus_sem); /*
Keith reports a use-after-free when a DPC event occurs concurrently to hot-removal of the same portion of the hierarchy: The dpc_handler() awaits readiness of the secondary bus below the Downstream Port where the DPC event occurred. To do so, it polls the config space of the first child device on the secondary bus. If that child device is concurrently removed, accesses to its struct pci_dev cause the kernel to oops. That's because pci_bridge_wait_for_secondary_bus() neglects to hold a reference on the child device. Before v6.3, the function was only called on resume from system sleep or on runtime resume. Holding a reference wasn't necessary back then because the pciehp IRQ thread could never run concurrently. (On resume from system sleep, IRQs are not enabled until after the resume_noirq phase. And runtime resume is always awaited before a PCI device is removed.) However starting with v6.3, pci_bridge_wait_for_secondary_bus() is also called on a DPC event. Commit 53b54ad074de ("PCI/DPC: Await readiness of secondary bus after reset"), which introduced that, failed to appreciate that pci_bridge_wait_for_secondary_bus() now needs to hold a reference on the child device because dpc_handler() and pciehp may indeed run concurrently. The commit was backported to v5.10+ stable kernels, so that's the oldest one affected. Add the missing reference acquisition. Abridged stack trace: BUG: unable to handle page fault for address: 00000000091400c0 CPU: 15 PID: 2464 Comm: irq/53-pcie-dpc 6.9.0 RIP: pci_bus_read_config_dword+0x17/0x50 pci_dev_wait() pci_bridge_wait_for_secondary_bus() dpc_reset_link() pcie_do_recovery() dpc_handler() Fixes: 53b54ad074de ("PCI/DPC: Await readiness of secondary bus after reset") Reported-by: Keith Busch <kbusch@kernel.org> Closes: https://lore.kernel.org/r/20240612181625.3604512-3-kbusch@meta.com/ Tested-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Lukas Wunner <lukas@wunner.de> Reviewed-by: Keith Busch <kbusch@kernel.org> Cc: stable@vger.kernel.org # v5.10+ --- drivers/pci/pci.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)