[+cc Linus -- FYI since I'm sure you'll see more reports of this; we call driver resume methods before they're prepared for it. We'll fix or revert this ASAP.] On Mon, Nov 08, 2021 at 12:58:25PM -0600, Bjorn Helgaas wrote: > [+cc Uwe, Rafael, linux-pm, linux-pci, linux-kernel, beginning of > thread: https://lore.kernel.org/linux-i2c/CAP145pgdrdiMAT7=-iB1DMgA7t_bMqTcJL4N0=6u8kNY3EU0dw@xxxxxxxxxxxxxx/T/#t] > > On Mon, Nov 08, 2021 at 05:34:14PM +0100, Robert Święcki wrote: > > > I'm daily-driving the linux from Linus' git (recompiling every day or > > > two), and yesterday it stopped booting. Below is the dmesg from > > > pstore. > > > ... > > > > This introduced the bug: 0c5c62ddf88c34bc83b66e4ac9beb2bb0e1887d4 > > https://github.com/torvalds/linux/commit/0c5c62ddf88c34bc83b66e4ac9beb2bb0e1887d4 > > Thank you very much for the debugging and this report! This report is > for i2c, but the problem will affect many drivers. > > > > <1>[ 1.431369][ T447] BUG: kernel NULL pointer dereference, > > > address: 0000000000000540 > > > <1>[ 1.431371][ T447] #PF: supervisor read access in kernel mode > > > <1>[ 1.431375][ T447] #PF: error_code(0x0000) - not-present page > > > <6>[ 1.431378][ T447] PGD 0 P4D 0 > > > <4>[ 1.431384][ T447] Oops: 0000 [#1] PREEMPT SMP NOPTI > > > <4>[ 1.431388][ T447] CPU: 12 PID: 447 Comm: systemd-udevd > > > Tainted: G E 5.15.0+ #91 > > > <4>[ 1.431391][ T447] Hardware name: ASUS System Product Name/ROG > > > CROSSHAIR VIII FORMULA, BIOS 3801 07/30/2021 > > > <4>[ 1.431392][ T447] RIP: 0010:i2c_dw_pci_resume+0x8/0x40 > > > [i2c_designware_pci] > > > <4>[ 1.431399][ T447] Code: 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 > > > 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 84 00 00 00 00 00 53 48 > > > 8b 5f 78 48 89 df <ff> 93 40 05 00 00 c6 83 c0 05 00 00 00 5b c3 66 66 > > > 2e 0f 1f 84 00 > > > <4>[ 1.431401][ T447] RSP: 0018:ffffb3e740a13ba8 EFLAGS: 00010286 > > > <4>[ 1.431403][ T447] RAX: 0000000000000000 RBX: 0000000000000000 > > > RCX: 0000000000000000 > > $ ./scripts/decodecode < oops > 22: 53 push %rbx > 23: 48 8b 5f 78 mov 0x78(%rdi),%rbx > 27: 48 89 df mov %rbx,%rdi > 2a:* ff 93 40 05 00 00 callq *0x540(%rbx) <-- trapping instruction > 30: c6 83 c0 05 00 00 00 movb $0x0,0x5c0(%rbx) > 37: 5b pop %rbx > 38: c3 retq > > static int i2c_dw_pci_resume(struct device *dev) > { > struct dw_i2c_dev *i_dev = dev_get_drvdata(dev); > int ret; > > ret = i_dev->init(i_dev); > i_dev->suspended = false; > > return ret; > > So I think we're trying to call i_dev->init(), which is a NULL > pointer. > > > > <4>[ 1.431422][ T447] pci_pm_runtime_resume+0xaa/0x100 > > > <4>[ 1.431434][ T447] __rpm_callback+0x3c/0x100 > > > <4>[ 1.431442][ T447] rpm_callback+0x54/0x80 > > > <4>[ 1.431445][ T447] rpm_resume+0x410/0x700 > > > <4>[ 1.431455][ T447] __pm_runtime_resume+0x45/0x80 > > > <4>[ 1.431457][ T447] pci_device_probe+0xa2/0x140 > > > <4>[ 1.431459][ T447] really_probe+0x1e4/0x400 > > > <4>[ 1.431464][ T447] __driver_probe_device+0xf9/0x180 > > > <4>[ 1.431466][ T447] driver_probe_device+0x19/0xc0 > > I think the problem here is that: > > - really_probe() sets dev->driver > > - local_pci_probe() calls pm_runtime_get_sync(), which leads to: > > - pci_pm_runtime_resume(), which previously skipped the driver's > .runtime_resume() method when "pci_dev->driver" as NULL > > - after 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of > pci_dev->driver") [1], it checks "dev->driver" instead of > "pci_dev->driver" > > - dev->driver is non-NULL (set by really_probe() above), but at this > point pci_dev->driver used to be NULL because local_pci_probe() > didn't set it until after after calling pm_runtime_get_sync() (see > b5f9c644eb1b ("PCI: Remove struct pci_dev->driver") [2]) > > - because dev->driver is non-NULL, we call i2c_dw_pci_resume() > before i2c_dw_pci_probe(), so the driver init hasn't been done > > Here's the call tree: > > really_probe > dev->driver = drv; # <-- > call_driver_probe > dev->bus->probe > pci_device_probe > __pci_device_probe > pci_call_probe > local_pci_probe > pm_runtime_get_sync > ... > pci_pm_runtime_resume > - if (!pci_dev->driver) # 2a4d9408c9e8 ("PCI: Use to_pci_driver() instead of pci_dev->driver") > + if (!to_pci_driver(dev->driver)) > return 0 > pm->runtime_resume > i2c_dw_pci_resume > i_dev->init() # <-- NULL ptr deref > - pci_dev->driver = pci_drv # b5f9c644eb1b ("PCI: Remove struct pci_dev->driver") > pci_drv->probe > i2c_dw_pci_probe > > Note that we used to call pm_runtime_get_sync() (and the driver's > runtime_resume() method) in the window where dev->driver had been set > but pci_dev->driver had not. Since we got rid of pci_dev->driver > altogether, that window no longer exists, so we call the driver's > runtime_resume() when it isn't prepared for it. > > [1] https://git.kernel.org/linus/2a4d9408c9e8 > [2] https://git.kernel.org/linus/b5f9c644eb1b
