From: Vishal Verma vishal.l.verma@intel.com
commit 71ee71d7adcba648077997a29a91158d20c40b09 upstream.
When an intermediate port's decoders have been exhausted by existing regions, and creating a new region with the port in question in it's hierarchical path is attempted, cxl_port_attach_region() fails to find a port decoder (as would be expected), and drops into the failure / cleanup path.
However, during cleanup of the region reference, a sanity check attempts to dereference the decoder, which in the above case didn't exist. This causes a NULL pointer dereference BUG.
To fix this, refactor the decoder allocation and de-allocation into helper routines, and in this 'free' routine, check that the decoder, @cxld, is valid before attempting any operations on it.
Cc: stable@vger.kernel.org Suggested-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Vishal Verma vishal.l.verma@intel.com Reviewed-by: Dave Jiang dave.jiang@intel.com Fixes: 384e624bb211 ("cxl/region: Attach endpoint decoders") Link: https://lore.kernel.org/r/20221101074100.1732003-1-vishal.l.verma@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cxl/core/region.c | 67 ++++++++++++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 26 deletions(-)
--- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -686,18 +686,27 @@ static struct cxl_region_ref *alloc_regi return cxl_rr; }
-static void free_region_ref(struct cxl_region_ref *cxl_rr) +static void cxl_rr_free_decoder(struct cxl_region_ref *cxl_rr) { - struct cxl_port *port = cxl_rr->port; struct cxl_region *cxlr = cxl_rr->region; struct cxl_decoder *cxld = cxl_rr->decoder;
+ if (!cxld) + return; + dev_WARN_ONCE(&cxlr->dev, cxld->region != cxlr, "region mismatch\n"); if (cxld->region == cxlr) { cxld->region = NULL; put_device(&cxlr->dev); } +}
+static void free_region_ref(struct cxl_region_ref *cxl_rr) +{ + struct cxl_port *port = cxl_rr->port; + struct cxl_region *cxlr = cxl_rr->region; + + cxl_rr_free_decoder(cxl_rr); xa_erase(&port->regions, (unsigned long)cxlr); xa_destroy(&cxl_rr->endpoints); kfree(cxl_rr); @@ -728,6 +737,33 @@ static int cxl_rr_ep_add(struct cxl_regi return 0; }
+static int cxl_rr_alloc_decoder(struct cxl_port *port, struct cxl_region *cxlr, + struct cxl_endpoint_decoder *cxled, + struct cxl_region_ref *cxl_rr) +{ + struct cxl_decoder *cxld; + + if (port == cxled_to_port(cxled)) + cxld = &cxled->cxld; + else + cxld = cxl_region_find_decoder(port, cxlr); + if (!cxld) { + dev_dbg(&cxlr->dev, "%s: no decoder available\n", + dev_name(&port->dev)); + return -EBUSY; + } + + if (cxld->region) { + dev_dbg(&cxlr->dev, "%s: %s already attached to %s\n", + dev_name(&port->dev), dev_name(&cxld->dev), + dev_name(&cxld->region->dev)); + return -EBUSY; + } + + cxl_rr->decoder = cxld; + return 0; +} + /** * cxl_port_attach_region() - track a region's interest in a port by endpoint * @port: port to add a new region reference 'struct cxl_region_ref' @@ -794,12 +830,6 @@ static int cxl_port_attach_region(struct cxl_rr->nr_targets++; nr_targets_inc = true; } - - /* - * The decoder for @cxlr was allocated when the region was first - * attached to @port. - */ - cxld = cxl_rr->decoder; } else { cxl_rr = alloc_region_ref(port, cxlr); if (IS_ERR(cxl_rr)) { @@ -810,26 +840,11 @@ static int cxl_port_attach_region(struct } nr_targets_inc = true;
- if (port == cxled_to_port(cxled)) - cxld = &cxled->cxld; - else - cxld = cxl_region_find_decoder(port, cxlr); - if (!cxld) { - dev_dbg(&cxlr->dev, "%s: no decoder available\n", - dev_name(&port->dev)); - goto out_erase; - } - - if (cxld->region) { - dev_dbg(&cxlr->dev, "%s: %s already attached to %s\n", - dev_name(&port->dev), dev_name(&cxld->dev), - dev_name(&cxld->region->dev)); - rc = -EBUSY; + rc = cxl_rr_alloc_decoder(port, cxlr, cxled, cxl_rr); + if (rc) goto out_erase; - } - - cxl_rr->decoder = cxld; } + cxld = cxl_rr->decoder;
rc = cxl_rr_ep_add(cxl_rr, cxled); if (rc) {