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cxl/region: Avoid null pointer dereference in region lookup

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[ 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>
This commit is contained in:
Alison Schofield 2024-06-03 17:36:09 -07:00 committed by Greg Kroah-Hartman
parent f12be1a1fd
commit a9e099e29e
1 changed files with 15 additions and 4 deletions
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19
drivers/cxl/core/region.c
View File

@ -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;
}