Thanks Thomas, With patch you suggested , panic has gone away from ' pci_find_next_ext_capability' as we not using inside aer_isr , but now it hits at pci_bus_read_config_dword. -------------------xxxxxxx bt og xxxxxxxx-----------------" PID: 24 TASK: ffff880274ac0000 CPU: 0 COMMAND: "kworker/0:1" #0 [ffff880274abbb18] machine_kexec at ffffffff8102cf18 #1 [ffff880274abbb78] crash_kexec at ffffffff810a6b05 #2 [ffff880274abbc40] oops_end at ffffffff8176d960 #3 [ffff880274abbc68] die at ffffffff810060db #4 [ffff880274abbc98] do_general_protection at ffffffff8176d452 #5 [ffff880274abbcc0] general_protection at ffffffff8176cdf2 [exception RIP: pci_bus_read_config_dword+100] RIP: ffffffff813405f4 RSP: ffff880274abbd70 RFLAGS: 00010046 RAX: 455a494c41495449 RBX: ffff880274891800 RCX: 0000000000000004 RDX: 0000000000000110 RSI: 0000000000000060 RDI: ffff880274891800 RBP: ffff880274abbd98 R8: ffff880274abbd7c R9: 00000000000011b5 R10: 0000000000000000 R11: 00000000000011b4 R12: ffff8802741a0210 R13: 0000000000000246 R14: ffff880272afc008 R15: ffff880272af8800 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #6 [ffff880274abbda0] get_device_error_info at ffffffff81356d74 #7 [ffff880274abbdd0] aer_isr at ffffffff81357b41 #8 [ffff880274abbe28] process_one_work at ffffffff8105d4c0 #9 [ffff880274abbe70] worker_thread at ffffffff8105e251 #10 [ffff880274abbed0] kthread at ffffffff81064260 #11 [ffff880274abbf50] ret_from_fork at ffffffff81773a38" -------------------xxxxxxx bt og end xxxxxxxx----------------- Regards, Gokul On Tue, Aug 7, 2018 at 9:00 PM, Thomas Tai wrote: > Hi Gokul, > Something pop up in my mind and want to share with you. I assume that your > device is not a root port device or a switch device. I assume when you > power off the device, a FATAL error is sent to the root port thus trigger > the aer_isr. > > Since it is a fatal error and your device is not a switch device, the code > should not reach out your device because fatal error means that the link to > your device is not reliable. So the pci_find_ext_capability() looks strange > to me. When compare the code with the master branch. v3.10 is missing > following patch. Would you think you can give it a try? > > commit 66b808099146166c44157600a166c8372172cd76 > Author: Keith Busch > Date: Tue Sep 27 16:23:34 2016 -0400 > > PCI/AER: Cache capability position > > Save the position of the error reporting capability so it doesn't need > to > be rediscovered during error handling. > > Signed-off-by: Keith Busch > Signed-off-by: Bjorn Helgaas > CC: Lukas Wunner > > - Thomas > > > On 08/06/2018 02:33 PM, gokul cg wrote: > >> Hi, >> >> I have tried with following patch and I am still getting same kernel >> panic. >> >> -------------X++++++++++++++++++++X--------------------- >> >> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c >> b/drivers/pci/pcie/aer/aerdrv_core.c >> index 0f4554e..05592aa 100644 >> --- a/drivers/pci/pcie/aer/aerdrv_core.c >> +++ b/drivers/pci/pcie/aer/aerdrv_core.c >> @@ -26,6 +26,7 @@ >> #include >> #include >> #include "aerdrv.h" >> +#include "../../pci.h" >> >> static bool forceload; >> static bool nosourceid; >> @@ -82,7 +82,7 @@ EXPORT_SYMBOL_GPL(pci_cleanup_ >> aer_uncorrect_error_status); >> static int add_error_device(struct aer_err_info *e_info, struct pci_dev >> *dev) >> { >> if (e_info->error_dev_num < AER_MAX_MULTI_ERR_DEVICES) { >> -e_info->dev[e_info->error_dev_num] = dev; >> +e_info->dev[e_info->error_dev_num] = pci_dev_get(dev); >> >> e_info->error_dev_num++; >> return 0; >> } >> @@ -659,6 +659,9 @@ static int get_device_error_info(struct pci_dev *dev, >> struct aer_err_info *info) >> if (!pos) >> return 1; >> >> + if (pci_dev_is_disconnected(dev)) >> + return 0; >> + >> if (info->severity == AER_CORRECTABLE) { >> pci_read_config_dword(dev, pos + PCI_ERR_COR_STATUS, >> &info->status); >> @@ -710,6 +713,8 @@ static inline void aer_process_err_devices(struct >> pcie_device *p_device, >> for (i = 0; i < e_info->error_dev_num && e_info->dev[i]; i++) { >> if (get_device_error_info(e_info->dev[i], e_info)) >> handle_error_source(p_device, e_info->dev[i], e_info); >> + >> + pci_dev_put(e_info->dev[i]); >> } >> } >> -------------X++++++++++++++++++++X--------------------- >> >> >> Note: I have configured CONFIG_HOTPLUG_PCI_PCIE and CONFIG_HOTPLUG_PCI as >> modules and loading in start up using script. >> >> root@/proc/:~# cat config | grep -i HOT >> CONFIG_TICK_ONESHOT=y >> CONFIG_HOTPLUG=y >> # CONFIG_MEMORY_HOTPLUG is not set >> CONFIG_HOTPLUG_CPU=y >> # CONFIG_BOOTPARAM_HOTPLUG_CPU0 is not set >> # CONFIG_DEBUG_HOTPLUG_CPU0 is not set >> CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y >> CONFIG_ACPI_HOTPLUG_CPU=y >> CONFIG_HOTPLUG_PCI_PCIE=m >> CONFIG_HOTPLUG_PCI=m >> # CONFIG_HOTPLUG_PCI_CPCI is not set >> # CONFIG_HOTPLUG_PCI_SHPC is not set >> CONFIG_DM_SNAPSHOT=y >> # CONFIG_USB_STORAGE_JUMPSHOT is not set >> # CONFIG_TRACER_SNAPSHOT is not set >> root@/proc/:~# >> >> Panic back trace : >> crash> bt >> PID: 24 TASK: ffff880274ac0000 CPU: 0 COMMAND: "kworker/0:1" >> #0 [ffff880274abbac8] machine_kexec at ffffffff8102cf18 >> #1 [ffff880274abbb28] crash_kexec at ffffffff810a6b05 >> #2 [ffff880274abbbf0] oops_end at ffffffff8176d8a0 >> #3 [ffff880274abbc18] die at ffffffff810060db >> #4 [ffff880274abbc48] do_general_protection at ffffffff8176d392 >> #5 [ffff880274abbc70] general_protection at ffffffff8176cd32 >> [exception RIP: pci_bus_read_config_dword+100] >> RIP: ffffffff813405f4 RSP: ffff880274abbd20 RFLAGS: 00010046 >> RAX: 435f494350006963 RBX: ffff880274891800 RCX: 0000000000000004 >> RDX: 0000000000000ffc RSI: 0000000000000060 RDI: ffff880274891800 >> RBP: ffff880274abbd48 R8: ffff880274abbd2c R9: 00000000000002b8 >> R10: ffff880274340000 R11: 0000000000000246 R12: ffff880274abbd5c >> R13: 0000000000000246 R14: 0000000000000000 R15: ffff880274920000 >> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >> #6 [ffff880274abbd50] pci_find_next_ext_capability at ffffffff81345db6 >> #7 [ffff880274abbd90] pci_find_ext_capability at ffffffff81347225 >> #8 [ffff880274abbda0] get_device_error_info at ffffffff81356c4d >> #9 [ffff880274abbdd0] aer_isr at ffffffff81357ab0 >> #10 [ffff880274abbe28] process_one_work at ffffffff8105d4c0 >> #11 [ffff880274abbe70] worker_thread at ffffffff8105e251 >> #12 [ffff880274abbed0] kthread at ffffffff81064260 >> #13 [ffff880274abbf50] ret_from_fork at ffffffff81773978 >> crash> >> >> >> Regards, >> Gokul >> >> On Thu, Aug 2, 2018 at 10:39 PM, Thomas Tai > > wrote: >> >> >> On 08/02/2018 11:07 AM, Lukas Wunner wrote: >> >> [cc += Thomas Tai] >> >> >> Hi Lukas, >> Thank you very much for cc me. >> >> >> On Thu, Aug 02, 2018 at 10:46:57AM +0200, Lukas Wunner wrote: >> >> On Thu, Aug 02, 2018 at 12:59:18PM +0530, gokul cg wrote: >> >> I am suspecting a possible race condition in the kernel >> between PCI driver >> and AER handling. >> >> >> The solution is to acquire a ref on each device in >> add_error_device(). >> Then release the ref aer_process_err_devices() by calling >> pci_dev_put(). >> >> >> So in case it wasn't clear, the below is what I had in mind. >> Completely untested though. Does this work for you? >> >> For v3.10 compatibility, cherry-pick 89ee9f768003 (or >> alternatively >> cherry-pick 8496e85c20e7 and replace pci_dev_is_disconnected(dev) >> with !pci_device_is_present(dev)). >> >> -- >8 -- >> Subject: [PATCH] PCI/AER: Fix use-after-free on surprise removal >> >> The work item to consume errors, aer_isr(), walks the hierarchy >> using >> pci_walk_bus() and stores a pointer to PCI devices which reported >> an >> error in an array. As long as pci_walk_bus() runs, those >> pointers are >> valid because pci_bus_sem is held. But once pci_walk_bus() >> finishes, >> nothing prevents the pointers from becoming invalid, e.g. through >> unplugging of the PCI devices. The unprotected pointers are then >> dereferenced in aer_process_err_devices(), which may oops: >> >> >> I like your idea to increment the refcount during pci_walk_bus(), >> that should fix the use-after-free issue. We just need Gokul to >> confirm if it fixes his issue or not. >> >> Thanks, >> Thomas >> >> >> >> #5 general_protection at ffffffff8176cdf2 >> [exception RIP: pci_bus_read_config_dword+100] >> #6 pci_find_next_ext_capability at ffffffff81345d7b >> #7 pci_find_ext_capability at ffffffff81347225 >> #8 get_device_error_info at ffffffff81356c4d >> #9 aer_isr at ffffffff81357a38 >> >> Fix by holding a ref on the devices until they have been >> processed. >> Skip processing of unplugged devices. >> >> Reported-by: gokul cg > > >> Signed-off-by: Lukas Wunner > > >> >> --- >> drivers/pci/pcie/aer.c | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c >> index a2e8838..937592e 100644 >> --- a/drivers/pci/pcie/aer.c >> +++ b/drivers/pci/pcie/aer.c >> @@ -657,7 +657,7 @@ void cper_print_aer(struct pci_dev *dev, int >> aer_severity, >> static int add_error_device(struct aer_err_info *e_info, >> struct pci_dev *dev) >> { >> if (e_info->error_dev_num < AER_MAX_MULTI_ERR_DEVICES) { >> - e_info->dev[e_info->error_dev_num] = dev; >> + e_info->dev[e_info->error_dev_num] = >> pci_dev_get(dev); >> e_info->error_dev_num++; >> return 0; >> } >> @@ -898,6 +898,9 @@ static int get_device_error_info(struct >> pci_dev *dev, struct aer_err_info *info) >> if (!pos) >> return 0; >> + if (pci_dev_is_disconnected(dev)) >> + return 0; >> + >> if (info->severity == AER_CORRECTABLE) { >> pci_read_config_dword(dev, pos + >> PCI_ERR_COR_STATUS, >> &info->status); >> @@ -948,6 +951,7 @@ static inline void >> aer_process_err_devices(struct aer_err_info *e_info) >> for (i = 0; i < e_info->error_dev_num && >> e_info->dev[i]; i++) { >> if (get_device_error_info(e_info->dev[i], >> e_info)) >> handle_error_source(e_info->dev[i], >> e_info); >> + pci_dev_put(e_info->dev[i]); >> } >> } >> >> >>