From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Subject: Re: [PATCH] PCI: pciehp: Differentiate between surprise and safe removal To: gokul cg Cc: Lukas Wunner , Mika Westerberg , Bjorn Helgaas , Ashok Raj , Keith Busch , Yinghai Lu , Sinan Kaya , linux-pci@vger.kernel.org, Alexandru Gagniuc References: <20180801164358.GI2534@lahna.fi.intel.com> <20180801171512.GA28440@wunner.de> <20180802072036.GN2534@lahna.fi.intel.com> <20180802084657.GA21267@wunner.de> <20180802150749.GA31683@wunner.de> From: Thomas Tai Message-ID: <1881c4f2-9502-bca8-3bac-089fdf6b43a4@oracle.com> Date: Tue, 7 Aug 2018 10:26:02 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed List-ID: 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. Sorry to hear that. What kernel message did you see before the crash. We assume the hotplug is corrupting the pci_dev, but is it really? Have you tried without insmod the hotplug provided that you can still power off the device via your I2C. > > -------------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]); >         } >   } > >