[+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
