6.6-stable review patch. If anyone has any objections, please let me know.
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From: Alison Schofield alison.schofield@intel.com
[ Upstream commit 285f2a08841432fc3e498b1cd00cce5216cdf189 ]
cxl_dpa_to_region() looks up a region based on a memdev and DPA. It wrongly assumes an endpoint found mapping the DPA is also of a fully assembled region. When not true it leads to a null pointer dereference looking up the region name.
This appears during testing of region lookup after a failure to assemble a BIOS defined region or if the lookup raced with the assembly of the BIOS defined region.
Failure to clean up BIOS defined regions that fail assembly is an issue in itself and a fix to that problem will alleviate some of the impact. It will not alleviate the race condition so let's harden this path.
The behavior change is that the kernel oops due to a null pointer dereference is replaced with a dev_dbg() message noting that an endpoint was mapped.
Additional comments are added so that future users of this function can more clearly understand what it provides.
Fixes: 0a105ab28a4d ("cxl/memdev: Warn of poison inject or clear to a mapped region") Signed-off-by: Alison Schofield alison.schofield@intel.com Reviewed-by: Jonathan Cameron Jonathan.Cameron@huawei.com Link: https://patch.msgid.link/20240604003609.202682-1-alison.schofield@intel.com Signed-off-by: Dave Jiang dave.jiang@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cxl/core/region.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index d2ce309434654..0d59af19ecee7 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -2518,22 +2518,33 @@ static int __cxl_dpa_to_region(struct device *dev, void *arg) { struct cxl_dpa_to_region_context *ctx = arg; struct cxl_endpoint_decoder *cxled; + struct cxl_region *cxlr; u64 dpa = ctx->dpa;
if (!is_endpoint_decoder(dev)) return 0;
cxled = to_cxl_endpoint_decoder(dev); - if (!cxled->dpa_res || !resource_size(cxled->dpa_res)) + if (!cxled || !cxled->dpa_res || !resource_size(cxled->dpa_res)) return 0;
if (dpa > cxled->dpa_res->end || dpa < cxled->dpa_res->start) return 0;
- dev_dbg(dev, "dpa:0x%llx mapped in region:%s\n", dpa, - dev_name(&cxled->cxld.region->dev)); + /* + * Stop the region search (return 1) when an endpoint mapping is + * found. The region may not be fully constructed so offering + * the cxlr in the context structure is not guaranteed. + */ + cxlr = cxled->cxld.region; + if (cxlr) + dev_dbg(dev, "dpa:0x%llx mapped in region:%s\n", dpa, + dev_name(&cxlr->dev)); + else + dev_dbg(dev, "dpa:0x%llx mapped in endpoint:%s\n", dpa, + dev_name(dev));
- ctx->cxlr = cxled->cxld.region; + ctx->cxlr = cxlr;
return 1; }