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Date:   Wed, 22 Mar 2023 18:21:11 +0100
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Jon Hunter <jonathanh@nvidia.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Rob Herring <robh+dt@kernel.org>, Andrew Lunn <andrew@lunn.ch>,
        Marek =?utf-8?B?QmVow7pu?= <marek.behun@nic.cz>,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH v2] PCI: Assign PCI domain by ida_alloc()
Message-ID: <20230322172111.a2dfp2eyicuskrez@pali>
References: <20220702204737.7719-1-pali@kernel.org>
 <20220714184130.5436-1-pali@kernel.org>
 <b529cb69-0602-9eed-fc02-2f068707a006@nvidia.com>
 <20230320205936.wd6pj3trljsduj5c@pali>
 <993ca7dc-1d39-6ae9-1033-838d81aeb076@nvidia.com>
 <3414723d-7d79-809f-e63f-35243d945b50@nvidia.com>
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On Wednesday 22 March 2023 14:36:23 Jon Hunter wrote:
> On 21/03/2023 18:44, Jon Hunter wrote:
> > 
> > On 20/03/2023 20:59, Pali Rohár wrote:
> > > Hello!
> > > 
> > > On Monday 20 March 2023 20:26:05 Jon Hunter wrote:
> > > > Hi Pali,
> > > > 
> > > > After this change was made we are seeing the following bug
> > > > report on a Tegra234 Jetson Orin board ...
> > > > 
> > > > [   17.172346] tegra194-pcie 141a0000.pcie: host bridge
> > > > /pcie@141a0000 ranges:
> > > > [   17.172470] tegra194-pcie 141a0000.pcie:      MEM
> > > > 0x2800000000..0x2b27ffffff -> 0x2800000000
> > > > [   17.172519] tegra194-pcie 141a0000.pcie:      MEM
> > > > 0x2b28000000..0x2b2fffffff -> 0x0040000000
> > > > [   17.172548] tegra194-pcie 141a0000.pcie:       IO
> > > > 0x003a100000..0x003a1fffff -> 0x003a100000
> > > > [   17.173449] tegra194-pcie 141a0000.pcie: iATU: unroll T, 8
> > > > ob, 2 ib, align 64K, limit 32G
> > > > [   18.279048] tegra194-pcie 141a0000.pcie: Phy link never came up
> > > > [   19.279285] tegra194-pcie 141a0000.pcie: Phy link never came up
> > > > [   19.279599] tegra194-pcie 141a0000.pcie: PCI host bridge to
> > > > bus 0005:00
> > > > [   19.279613] pci_bus 0005:00: root bus resource [bus 00-ff]
> > > > [   19.279622] pci_bus 0005:00: root bus resource [mem
> > > > 0x2800000000-0x2b27ffffff pref]
> > > > [   19.279631] pci_bus 0005:00: root bus resource [mem
> > > > 0x2b28000000-0x2b2fffffff] (bus address [0x40000000-0x47ffffff])
> > > > [   19.279639] pci_bus 0005:00: root bus resource [io
> > > > 0x200000-0x2fffff] (bus address [0x3a100000-0x3a1fffff])
> > > > [   19.279687] pci 0005:00:00.0: [10de:229a] type 01 class 0x060400
> > > > [   19.279886] pci 0005:00:00.0: PME# supported from D0 D3hot
> > > > [   19.283256] pci 0005:00:00.0: PCI bridge to [bus 01-ff]
> > > > [   19.283590] pcieport 0005:00:00.0: Adding to iommu group 26
> > > > [   19.283991] pcieport 0005:00:00.0: PME: Signaling with IRQ 174
> > > > [   19.284429] pcieport 0005:00:00.0: AER: enabled with IRQ 174
> > > > [   19.285003] pci_bus 0005:01: busn_res: [bus 01-ff] is released
> > > > [   19.285591] pci 0005:00:00.0: Removing from iommu group 26
> > > > [   19.285751] pci_bus 0005:00: busn_res: [bus 00-ff] is released
> > > > [   19.285870]
> > > > ==================================================================
> > > > [   19.293351] BUG: KFENCE: use-after-free read in
> > > > pci_bus_release_domain_nr+0x10/0x70
> > > > 
> > > > [   19.302817] Use-after-free read at 0x000000007f3b80eb (in
> > > > kfence-#115):
> > > > [   19.309677]  pci_bus_release_domain_nr+0x10/0x70
> > > > [   19.309691]  dw_pcie_host_deinit+0x28/0x78
> > > > [   19.309702]  tegra_pcie_deinit_controller+0x1c/0x38 [pcie_tegra194]
> > > > [   19.309734]  tegra_pcie_dw_probe+0x648/0xb28 [pcie_tegra194]
> > > > [   19.309752]  platform_probe+0x90/0xd8
> > > > [   19.309764]  really_probe+0xb8/0x298
> > > > [   19.309777]  __driver_probe_device+0x78/0xd8
> > > > [   19.309788]  driver_probe_device+0x38/0x120
> > > > [   19.309799]  __device_attach_driver+0x94/0xe0
> > > > [   19.309812]  bus_for_each_drv+0x70/0xc8
> > > > [   19.309822]  __device_attach+0xfc/0x188
> > > > [   19.309833]  device_initial_probe+0x10/0x18
> > > > [   19.309844]  bus_probe_device+0x94/0xa0
> > > > [   19.309854]  deferred_probe_work_func+0x80/0xb8
> > > > [   19.309864]  process_one_work+0x1e0/0x348
> > > > [   19.309882]  worker_thread+0x48/0x410
> > > > [   19.309891]  kthread+0xf4/0x110
> > > > [   19.309904]  ret_from_fork+0x10/0x20
> > > > 
> > > > [   19.311457] kfence-#115:
> > > > 0x00000000063a155a-0x00000000ba698da8, size=1072,
> > > > cache=kmalloc-2k
> > > > 
> > > > [   19.311469] allocated by task 96 on cpu 10 at 19.279323s:
> > > > [   19.311562]  __kmem_cache_alloc_node+0x260/0x278
> > > > [   19.311571]  kmalloc_trace+0x24/0x30
> > > > [   19.311580]  pci_alloc_bus+0x24/0xa0
> > > > [   19.311590]  pci_register_host_bridge+0x48/0x4b8
> > > > [   19.311601]  pci_scan_root_bus_bridge+0xc0/0xe8
> > > > [   19.311613]  pci_host_probe+0x18/0xc0
> > > > [   19.311623]  dw_pcie_host_init+0x2c0/0x568
> > > > [   19.311630]  tegra_pcie_dw_probe+0x610/0xb28 [pcie_tegra194]
> > > > [   19.311647]  platform_probe+0x90/0xd8
> > > > [   19.311653]  really_probe+0xb8/0x298
> > > > [   19.311663]  __driver_probe_device+0x78/0xd8
> > > > [   19.311672]  driver_probe_device+0x38/0x120
> > > > [   19.311682]  __device_attach_driver+0x94/0xe0
> > > > [   19.311694]  bus_for_each_drv+0x70/0xc8
> > > > [   19.311702]  __device_attach+0xfc/0x188
> > > > [   19.311713]  device_initial_probe+0x10/0x18
> > > > [   19.311724]  bus_probe_device+0x94/0xa0
> > > > [   19.311733]  deferred_probe_work_func+0x80/0xb8
> > > > [   19.311743]  process_one_work+0x1e0/0x348
> > > > [   19.311753]  worker_thread+0x48/0x410
> > > > [   19.311763]  kthread+0xf4/0x110
> > > > [   19.311771]  ret_from_fork+0x10/0x20
> > > > 
> > > > [   19.311782] freed by task 96 on cpu 10 at 19.285833s:
> > > > [   19.311799]  release_pcibus_dev+0x30/0x40
> > > > [   19.311808]  device_release+0x30/0x90
> > > > [   19.311814]  kobject_put+0xa8/0x120
> > > > [   19.311832]  device_unregister+0x20/0x30
> > > > [   19.311839]  pci_remove_bus+0x78/0x88
> > > > [   19.311850]  pci_remove_root_bus+0x5c/0x98
> > > > [   19.311860]  dw_pcie_host_deinit+0x28/0x78
> > > > [   19.311866]  tegra_pcie_deinit_controller+0x1c/0x38 [pcie_tegra194]
> > > > [   19.311883]  tegra_pcie_dw_probe+0x648/0xb28 [pcie_tegra194]
> > > > [   19.311900]  platform_probe+0x90/0xd8
> > > > [   19.311906]  really_probe+0xb8/0x298
> > > > [   19.311916]  __driver_probe_device+0x78/0xd8
> > > > [   19.311926]  driver_probe_device+0x38/0x120
> > > > [   19.311936]  __device_attach_driver+0x94/0xe0
> > > > [   19.311947]  bus_for_each_drv+0x70/0xc8
> > > > [   19.311956]  __device_attach+0xfc/0x188
> > > > [   19.311966]  device_initial_probe+0x10/0x18
> > > > [   19.311976]  bus_probe_device+0x94/0xa0
> > > > [   19.311985]  deferred_probe_work_func+0x80/0xb8
> > > > [   19.311995]  process_one_work+0x1e0/0x348
> > > > [   19.312005]  worker_thread+0x48/0x410
> > > > [   19.312014]  kthread+0xf4/0x110
> > > > [   19.312022]  ret_from_fork+0x10/0x20
> > > 
> > > Based on the above trace it looks like a double free of "pp->bridge"
> > > structure.
> > > 
> > > Also, which kernel version are you using? Because from above third
> > > trace it looks like that dw_pcie_host_deinit() calls first
> > > pci_remove_root_bus() function and then (from first strace) it also
> > > calls pci_bus_release_domain_nr() function.
> > 
> > 
> > I have definitely seen this with v6.2. I was doing some more testing and
> >  now it appears that the issue is somewhat intermittent. So now I am no
> > longer confident that reverting this change does fix it. The backtrace
> > made it seem like this is a likely candidate, but I need to do more
> > testing.
> 
> 
> OK, so I have done some more testing. I found that if I build the Tegra194
> PCIe driver into the kernel, then I can reproduce the above 100%. I guess by
> loading early there is more chance of a probe deferral. With that I verified
> that the issue is seen on v6.2 (as I previously observed) and on v6.3-rc3.
> Reverting this commit on top of v6.3-rc3 fixes this and I no longer see the
> problem.
> 
> Let me know if you have any thoughts on how to fix this.
> 
> Thanks
> Jon
> 
> -- 
> nvpublic

Sorry, but I'm not going to investigate another issue in this area.
I spent too much time in debugging issues, prepared fixes and the only
result was simple silence, rejection and proposal to resend emails.
The only thing which I receive are bug reports from the users and I
really do not want to repeat reply, hey patch for this was sent to
mailing list... So I do not see reason why I should look at this issue
as with high probability result would be same... for which I'm not
interested.