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Message-ID: <20221215170909.2650271-1-fan.ni@samsung.com>
Date: Thu, 15 Dec 2022 17:09:14 +0000
From: Fan Ni <fan.ni@...sung.com>
To: "alison.schofield@...el.com" <alison.schofield@...el.com>,
"vishal.l.verma@...el.com" <vishal.l.verma@...el.com>,
"ira.weiny@...el.com" <ira.weiny@...el.com>,
"bwidawsk@...nel.org" <bwidawsk@...nel.org>,
"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
"Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>,
"dan.carpenter@...cle.com" <dan.carpenter@...cle.com>
CC: "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
Adam Manzanares <a.manzanares@...sung.com>,
"dave@...olabs.net" <dave@...olabs.net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Fan Ni <fan.ni@...sung.com>
Subject: [PATCH] cxl/region: Fix null pointer dereference for resetting
decoder
Not all decoders have a reset callback.
The CXL specification allows a host bridge with a single root port to
have no explicit HDM decoders. Currently the region driver assumes there
are none. As such the CXL core creates a special pass through decoder
instance without a commit/reset callback.
Prior to this patch, the ->reset() callback was called unconditionally when
calling cxl_region_decode_reset. Thus a configuration with 1 Host Bridge,
1 Root Port, and one directly attached CXL type 3 device or multiple CXL
type 3 devices attached to downstream ports of a switch can cause a null
pointer dereference.
Before the fix, a kernel crash was observed when we destroy the region, and
a pass through decoder is reset.
The issue can be reproduced as below,
1) create a region with a CXL setup which includes a HB with a
single root port under which a memdev is attached directly.
2) destroy the region with cxl destroy-region regionX -f.
Fixes: 176baefb2eb5 ("cxl/hdm: Commit decoder state to hardware")
Signed-off-by: Fan Ni <fan.ni@...sung.com>
---
drivers/cxl/core/region.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index f9ae5ad284ff..3931793a13ac 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -131,7 +131,7 @@ static int cxl_region_decode_reset(struct cxl_region *cxlr, int count)
struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
struct cxl_port *iter = cxled_to_port(cxled);
struct cxl_ep *ep;
- int rc;
+ int rc = 0;
while (!is_cxl_root(to_cxl_port(iter->dev.parent)))
iter = to_cxl_port(iter->dev.parent);
@@ -143,7 +143,8 @@ static int cxl_region_decode_reset(struct cxl_region *cxlr, int count)
cxl_rr = cxl_rr_load(iter, cxlr);
cxld = cxl_rr->decoder;
- rc = cxld->reset(cxld);
+ if (cxld->reset)
+ rc = cxld->reset(cxld);
if (rc)
return rc;
}
@@ -186,7 +187,8 @@ static int cxl_region_decode_commit(struct cxl_region *cxlr)
iter = ep->next, ep = cxl_ep_load(iter, cxlmd)) {
cxl_rr = cxl_rr_load(iter, cxlr);
cxld = cxl_rr->decoder;
- cxld->reset(cxld);
+ if (cxld->reset)
+ cxld->reset(cxld);
}
cxled->cxld.reset(&cxled->cxld);
--
2.25.1
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