linux-kernel - Re: [PATCH v7 01/17] PCI/DPC: Initialize aer_err

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Message-ID: <20250521191803.GA1426656@bhelgaas>
Date: Wed, 21 May 2025 14:18:03 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-pci@...r.kernel.org, Jon Pan-Doh <pandoh@...gle.com>,
	Karolina Stolarek <karolina.stolarek@...cle.com>,
	Weinan Liu <wnliu@...gle.com>,
	Martin Petersen <martin.petersen@...cle.com>,
	Ben Fuller <ben.fuller@...cle.com>,
	Drew Walton <drewwalton@...rosoft.com>,
	Anil Agrawal <anilagrawal@...a.com>,
	Tony Luck <tony.luck@...el.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Lukas Wunner <lukas@...ner.de>, Sargun Dhillon <sargun@...a.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Kai-Heng Feng <kaihengf@...dia.com>,
	Keith Busch <kbusch@...nel.org>, Robert Richter <rrichter@....com>,
	Terry Bowman <terry.bowman@....com>,
	Shiju Jose <shiju.jose@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>
Subject: Re: [PATCH v7 01/17] PCI/DPC: Initialize aer_err_info before using it

On Wed, May 21, 2025 at 09:52:18AM +0100, Jonathan Cameron wrote:
> On Tue, 20 May 2025 16:50:18 -0500
> Bjorn Helgaas <helgaas@...nel.org> wrote:
> 
> > From: Bjorn Helgaas <bhelgaas@...gle.com>
> > 
> > Previously the struct aer_err_info "info" was allocated on the stack
> > without being initialized, so it contained junk except for the fields we
> > explicitly set later.
> > 
> > Initialize "info" at declaration so it starts as all zeros.
> > 
> > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > Tested-by: Krzysztof Wilczyński <kwilczynski@...nel.org>
> > Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> I chased this through a bit and looks like at least some unset fields would
> result in garbage prints.  So maybe needs a fixes tag?
> info->tlp_header_valid is an easy one to follow as only set in some paths.

I don't see a current issue related to info->tlp_header_valid because
it's always cleared in the path from DPC:

  dpc_process_error
    dpc_get_aer_uncorrect_severity
      info->severity = AER_FATAL or AER_NONFATAL
    aer_get_device_error_info
      info->status = 0;
      info->tlp_header_valid = 0;    # unconditional
      pci_read_config_dword(PCI_ERR_UNCOR_STATUS, &info->status);
      pci_read_config_dword(PCI_ERR_UNCOR_MASK, &info->mask);
      info->first_error = PCI_ERR_CAP_FEP(...);
    aer_print_error

However, only info->{severity,status,tlp_header_valid,mask,
first_error} are initialized before dpc_process_error() calls
aer_print_error(), and aer_print_error() uses info->{id,
error_dev_num}, which haven't been initialized.

AFAICT, this has been the case since
https://git.kernel.org/linus/8aefa9b0d910 ("PCI/DPC: Print AER status
in DPC event handling")

Here's aer_get_device_error_info() at that time:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/pcie/aer.c?id=8aefa9b0d910#n867

and aer_print_error():
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/pcie/aer.c?id=8aefa9b0d910#n530

At the time of 8aefa9b0d910, info->severity was also used without
initialization; this was fixed by 9f08a5d896ce ("PCI/DPC: Fix print
AER status in DPC event handling").

But I think the info->{id,error_dev_num} has been there since.

Anyway, I added:

  Fixes: 8aefa9b0d910 ("PCI/DPC: Print AER status in DPC event handling")

> Otherwise absolutely makes sense.
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > ---
> >  drivers/pci/pcie/dpc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> > index df42f15c9829..3daaf61c79c9 100644
> > --- a/drivers/pci/pcie/dpc.c
> > +++ b/drivers/pci/pcie/dpc.c
> > @@ -258,7 +258,7 @@ static int dpc_get_aer_uncorrect_severity(struct pci_dev *dev,
> >  void dpc_process_error(struct pci_dev *pdev)
> >  {
> >  	u16 cap = pdev->dpc_cap, status, source, reason, ext_reason;
> > -	struct aer_err_info info;
> > +	struct aer_err_info info = {};
> >  
> >  	pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> >  	pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID, &source);
>