On Thu, Oct 8, 2020 at 1:24 AM Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxx> wrote: > > > On 10/7/20 4:31 AM, Ethan Zhao wrote: > > During DPC error injection test we found there is race condition between > > pciehp and DPC driver, NULL pointer dereference caused panic as following > > > > # setpci -s 64:02.0 0x196.w=000a > > // 64:02.0 is rootport has DPC capability > > # setpci -s 65:00.0 0x04.w=0544 > > // 65:00.0 is NVMe SSD populated in above port > > # mount /dev/nvme0n1p1 nvme > > > > (tested on stable 5.8 & ICS(Ice Lake SP platform, see > > https://en.wikichip.org/wiki/intel/microarchitectures/ice_lake_(server)) > > > > BUG: kernel NULL pointer dereference, address: 0000000000000050 > > ... > > CPU: 12 PID: 513 Comm: irq/124-pcie-dp Not tainted 5.8.0-0.0.7.el8.x86_64+ #1 > > RIP: 0010:report_error_detected.cold.4+0x7d/0xe6 > > Code: b6 d0 e8 e8 fe 11 00 e8 16 c5 fb ff be 06 00 00 00 48 89 df e8 d3 65 ff > > ff b8 06 00 00 00 e9 75 fc ff ff 48 8b 43 68 45 31 c9 <48> 8b 50 50 48 83 3a 00 > > 41 0f 94 c1 45 31 c0 48 85 d2 41 0f 94 c0 > > RSP: 0018:ff8e06cf8762fda8 EFLAGS: 00010246 > > RAX: 0000000000000000 RBX: ff4e3eaacf42a000 RCX: ff4e3eb31f223c01 > > RDX: ff4e3eaacf42a140 RSI: ff4e3eb31f223c00 RDI: ff4e3eaacf42a138 > > RBP: ff8e06cf8762fdd0 R08: 00000000000000bf R09: 0000000000000000 > > R10: 000000eb8ebeab53 R11: ffffffff93453258 R12: 0000000000000002 > > R13: ff4e3eaacf42a130 R14: ff8e06cf8762fe2c R15: ff4e3eab44733828 > > FS: 0000000000000000(0000) GS:ff4e3eab1fd00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000050 CR3: 0000000f8f80a004 CR4: 0000000000761ee0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > PKRU: 55555554 > > Call Trace: > > ? report_normal_detected+0x20/0x20 > > report_frozen_detected+0x16/0x20 > > pci_walk_bus+0x75/0x90 > > ? dpc_irq+0x90/0x90 > > pcie_do_recovery+0x157/0x201 > > ? irq_finalize_oneshot.part.47+0xe0/0xe0 > > dpc_handler+0x29/0x40 > > irq_thread_fn+0x24/0x60 > > ... > > > > Debug shows when port DPC feature was enabled and triggered by errors, > > DLLSC/PDC/DPC interrupts will be sent to pciehp and DPC driver almost > > at the same time, and no delay between them is required by specification. > > so DPC driver and pciehp drivers may handle these interrupts cocurrently. > > > > While DPC driver is doing pci_walk_bus() and calling device driver's > > callback without pci_dev_get() to increase device reference count, the > > device and its driver instance are likely being freed by > > pci_stop_and_removed_bus_device() > > -> pci_dev_put(). > > > > So does pci_dev_get() before using the device instance to avoid NULL > > pointer dereference. > Won't it be better if you get this in pcie_do_recovery()? Don't think so, just like lock, we should keep the scope with lock protected as small as possible. Locking a big area unnecessarily isn't acceptable. Thanks, Ethan > > > > Signed-off-by: Ethan Zhao <haifeng.zhao@xxxxxxxxx> > > Tested-by: Wen Jin <wen.jin@xxxxxxxxx> > > Tested-by: Shanshan Zhang <ShanshanX.Zhang@xxxxxxxxx> > > --- > > Changes: > > v2: revise doc according to Andy's suggestion. > > v3: no change. > > v4: no change. > > v5: no change. > > v6: moved to [1/5] from [3/5] and revised comment according to Lukas' > > suggestion. > > v7: no change. > > v8: no change. > > > > drivers/pci/pcie/err.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c > > index c543f419d8f9..e35c4480c86b 100644 > > --- a/drivers/pci/pcie/err.c > > +++ b/drivers/pci/pcie/err.c > > @@ -52,6 +52,8 @@ static int report_error_detected(struct pci_dev *dev, > > pci_ers_result_t vote; > > const struct pci_error_handlers *err_handler; > > > > + if (!pci_dev_get(dev)) > > + return 0; > > device_lock(&dev->dev); > > if (!pci_dev_set_io_state(dev, state) || > > !dev->driver || > > @@ -76,6 +78,7 @@ static int report_error_detected(struct pci_dev *dev, > > pci_uevent_ers(dev, vote); > > *result = merge_result(*result, vote); > > device_unlock(&dev->dev); > > + pci_dev_put(dev); > > return 0; > > } > > > > @@ -94,6 +97,8 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data) > > pci_ers_result_t vote, *result = data; > > const struct pci_error_handlers *err_handler; > > > > + if (!pci_dev_get(dev)) > > + return 0; > > device_lock(&dev->dev); > > if (!dev->driver || > > !dev->driver->err_handler || > > @@ -105,6 +110,7 @@ static int report_mmio_enabled(struct pci_dev *dev, void *data) > > *result = merge_result(*result, vote); > > out: > > device_unlock(&dev->dev); > > + pci_dev_put(dev); > > return 0; > > } > > > > @@ -113,6 +119,8 @@ static int report_slot_reset(struct pci_dev *dev, void *data) > > pci_ers_result_t vote, *result = data; > > const struct pci_error_handlers *err_handler; > > > > + if (!pci_dev_get(dev)) > > + return 0; > > device_lock(&dev->dev); > > if (!dev->driver || > > !dev->driver->err_handler || > > @@ -124,6 +132,7 @@ static int report_slot_reset(struct pci_dev *dev, void *data) > > *result = merge_result(*result, vote); > > out: > > device_unlock(&dev->dev); > > + pci_dev_put(dev); > > return 0; > > } > > > > @@ -131,6 +140,8 @@ static int report_resume(struct pci_dev *dev, void *data) > > { > > const struct pci_error_handlers *err_handler; > > > > + if (!pci_dev_get(dev)) > > + return 0; > > device_lock(&dev->dev); > > if (!pci_dev_set_io_state(dev, pci_channel_io_normal) || > > !dev->driver || > > @@ -143,6 +154,7 @@ static int report_resume(struct pci_dev *dev, void *data) > > out: > > pci_uevent_ers(dev, PCI_ERS_RESULT_RECOVERED); > > device_unlock(&dev->dev); > > + pci_dev_put(dev); > > return 0; > > } > > > > -- > Sathyanarayanan Kuppuswamy > Linux Kernel Developer >
