linux-kernel - Re: [PATCH] testing/cxl: Fix abused pci_bus_read_config

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Message-ID: <87o73k7fg2.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Wed, 16 Oct 2024 14:02:53 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Li Zhijian <lizhijian@...itsu.com>
Cc: linux-cxl@...r.kernel.org,  Davidlohr Bueso <dave@...olabs.net>,
  Jonathan Cameron <jonathan.cameron@...wei.com>,  Dave Jiang
 <dave.jiang@...el.com>,  Alison Schofield <alison.schofield@...el.com>,
  Vishal Verma <vishal.l.verma@...el.com>,  Ira Weiny
 <ira.weiny@...el.com>,  Dan Williams <dan.j.williams@...el.com>,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] testing/cxl: Fix abused pci_bus_read_config_word() on
 platform device

Hi, Zhijian,

Li Zhijian <lizhijian@...itsu.com> writes:

> The cxl_region_shared_upstream_bandwidth_update() in clx_core works on
> PCI/PCIe CXL device only while cxl_test was implemeneted by platform
> device.
>
> Mock a cxl_region_shared_upstream_bandwidth_update() which does nothing
> for cxl_core so that the cxl_test goes well.
>
> Abuse cxl_region_shared_upstream_bandwidth_update() on platform device
> will cause a kernel panic with calltrace:
>  platform cxl_host_bridge.3: host supports CXL (restricted)
>  Oops: general protection fault, probably for non-canonical address 0x3ef17856fcae4fbd: 0000 [#1] PREEMPT SMP PTI
>  CPU: 1 UID: 0 PID: 9167 Comm: cxl Kdump: loaded Tainted: G           OE      6.12.0-rc3-master+ #66
>  Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
>  Hardware name: LENOVO 90CXCTO1WW/, BIOS FCKT70AUS 04/23/2015
>  RIP: 0010:pci_bus_read_config_word+0x1c/0x60
>  Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 53 b8 87 00 00 00 48 83 ec 08 c7 44 24 04 00 00 00 00 f6 c2 01 75 29 <48> 8b 87 c0 00 00 00 48 89 cb 4c 8d 44 24 04 b9 02 00 00 00 48 8b
>  RSP: 0018:ffffa115034dfbb8 EFLAGS: 00010246
>  RAX: 0000000000000087 RBX: 0000000000000012 RCX: ffffa115034dfbfe
>  RDX: 0000000000000016 RSI: 000000006f4e2f4e RDI: 3ef17856fcae4efd
>  RBP: ffff8cc229121b48 R08: 0000000000000010 R09: 0000000000000000
>  R10: 0000000000000001 R11: ffff8cc225434360 R12: ffffa115034dfbfe
>  R13: 0000000000000000 R14: ffff8cc2f119a080 R15: ffffa115034dfc50
>  FS:  00007f31d93537c0(0000) GS:ffff8cc510a80000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 00007f31d95f3370 CR3: 00000001163ea001 CR4: 00000000001726f0
>  Call Trace:
>   <TASK>
>   ? __die_body.cold+0x19/0x27
>   ? die_addr+0x38/0x60
>   ? exc_general_protection+0x1f5/0x4b0
>   ? asm_exc_general_protection+0x22/0x30
>   ? pci_bus_read_config_word+0x1c/0x60
>   pcie_capability_read_word+0x93/0xb0
>   pcie_link_speed_mbps+0x18/0x50
>   cxl_pci_get_bandwidth+0x18/0x60 [cxl_core]
>   cxl_endpoint_gather_bandwidth.constprop.0+0xf4/0x230 [cxl_core]
>   ? xas_store+0x54/0x660
>   ? preempt_count_add+0x69/0xa0
>   ? _raw_spin_lock+0x13/0x40
>   ? __kmalloc_cache_noprof+0xe7/0x270
>   cxl_region_shared_upstream_bandwidth_update+0x9c/0x790 [cxl_core]
>   cxl_region_attach+0x520/0x7e0 [cxl_core]
>   store_targetN+0xf2/0x120 [cxl_core]
>   kernfs_fop_write_iter+0x13a/0x1f0
>   vfs_write+0x23b/0x410
>   ksys_write+0x53/0xd0
>   do_syscall_64+0x62/0x180
>   entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> And Ying also reported a KASAN error with similar calltrace.
>
> Reported-by: "Huang, Ying" <ying.huang@...el.com>
> Closes: https://lore.kernel.org/linux-cxl/87y12w9vp5.fsf@yhuang6-desk2.ccr.corp.intel.com/
> Fixes: a5ab0de0ebaa ("cxl: Calculate region bandwidth of targets with shared upstream link")
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>

This fixes the KASAN error report in my test too.  Thanks!  Feel free to
add

Tested-by: "Huang, Ying" <ying.huang@...el.com>

--
Best Regards,
Huang, Ying