[PATCH v3] cxl/core: Return error when cxl_endpoint_gather_bandwidth() handles a non-PCI device

From: Li Zhijian
Date: Mon Oct 21 2024 - 23:01:42 EST


The function cxl_endpoint_gather_bandwidth() invokes
pci_bus_read/write_XXX(), however, not all CXL devices are presently
implemented via PCI. It is recognized that the cxl_test has realized a CXL
device using a platform device.

Calling pci_bus_read/write_XXX() in cxl_test will cause kernel panic:
platform cxl_host_bridge.3: host supports CXL (restricted)
Oops: general protection fault, probably for non-canonical address 0x3ef17856fcae4fbd: 0000 [#1] PREEMPT SMP PTI
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@xxxxxxxxx>
Closes: http://lore.kernel.org/87y12w9vp5.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: a5ab0de0ebaa ("cxl: Calculate region bandwidth of targets with shared upstream link")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
V3:
update return code to ENODEV and change logs #Dan

V2:
Check device type in original cxl_endpoint_gather_bandwidth() instead of mocking a new one. # Dan
Also noticed that the existing cxl_switch_gather_bandwidth() also have the same check.
---
drivers/cxl/core/cdat.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
index ef1621d40f05..e9cd7939c407 100644
--- a/drivers/cxl/core/cdat.c
+++ b/drivers/cxl/core/cdat.c
@@ -641,6 +641,9 @@ static int cxl_endpoint_gather_bandwidth(struct cxl_region *cxlr,
void *ptr;
int rc;

+ if (!dev_is_pci(cxlds->dev))
+ return -ENODEV;
+
if (cxlds->rcd)
return -ENODEV;

--
2.44.0