This is a note to let you know that I've just added the patch titled
cxl/region: Fix null pointer dereference for resetting decoder
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cxl-region-fix-null-pointer-dereference-for-resetting-decoder.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4fa4302d6dc7de7e8e74dc7405611a2efb4bf54b Mon Sep 17 00:00:00 2001
From: Fan Ni <fan.ni@xxxxxxxxxxx>
Date: Thu, 15 Dec 2022 17:09:14 +0000
Subject: cxl/region: Fix null pointer dereference for resetting decoder
From: Fan Ni <fan.ni@xxxxxxxxxxx>
commit 4fa4302d6dc7de7e8e74dc7405611a2efb4bf54b upstream.
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")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Fan Ni <fan.ni@xxxxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Tested-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Reviewed-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221215170909.2650271-1-fan.ni@xxxxxxxxxxx
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 02f28da519e3..02275e6b621b 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);
--
2.39.1
Patches currently in stable-queue which might be from fan.ni@xxxxxxxxxxx are
queue-6.1/cxl-region-fix-null-pointer-dereference-for-resetting-decoder.patch
