[PATCH 1/2] mtd: spinand: fix NULL pointer dereference with no ECC engine

[Nuno Sá]

When "nand-no-ecc-engine" is set in DT, nanddev_get_ecc_engine() takes
the NAND_ECC_ENGINE_TYPE_NONE path and returns success while leaving
nand->ecc.engine NULL. The SPI-NAND code nevertheless dereferences it
unconditionally to test for a pipelined engine, so probing such a
device oopses immediately.

Rather than open-coding the test three times, add a
nand_ecc_is_pipelined() helper to the NAND core that folds the NULL
check into the integration comparison, and use it everywhere. Future
callers then cannot reintroduce the problem.

Fixes: f9d7c7265bcf ("mtd: spinand: Create direct mapping descriptors for ECC operations")
Cc: stable at vger.kernel.org
Signed-off-by: Nuno Sá <nuno.sa at analog.com>
---
 drivers/mtd/nand/ecc.c      | 7 +++++++
 drivers/mtd/nand/spi/core.c | 8 +++-----
 include/linux/mtd/nand.h    | 2 ++
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/ecc.c b/drivers/mtd/nand/ecc.c
index 6ccdff3fc913..1d809cbd47e6 100644
--- a/drivers/mtd/nand/ecc.c
+++ b/drivers/mtd/nand/ecc.c
@@ -159,6 +159,13 @@ int nand_ecc_finish_io_req(struct nand_device *nand,
 }
 EXPORT_SYMBOL(nand_ecc_finish_io_req);
 
+bool nand_ecc_is_pipelined(const struct nand_device *nand)
+{
+	return nand->ecc.engine &&
+	       nand->ecc.engine->integration == NAND_ECC_ENGINE_INTEGRATION_PIPELINED;
+}
+EXPORT_SYMBOL(nand_ecc_is_pipelined);
+
 /* Define default OOB placement schemes for large and small page devices */
 static int nand_ooblayout_ecc_sp(struct mtd_info *mtd, int section,
 				 struct mtd_oob_region *oobregion)
diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 35365b67dd8e..03ff43445693 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -508,8 +508,7 @@ static int spinand_read_from_cache_op(struct spinand_device *spinand,
 	else
 		rdesc->info.op_tmpl = &rdesc->info.primary_op_tmpl;
 
-	if (nand->ecc.engine->integration == NAND_ECC_ENGINE_INTEGRATION_PIPELINED &&
-	    req->mode != MTD_OPS_RAW)
+	if (nand_ecc_is_pipelined(nand) && req->mode != MTD_OPS_RAW)
 		rdesc->info.op_tmpl->data.ecc = true;
 	else
 		rdesc->info.op_tmpl->data.ecc = false;
@@ -603,8 +602,7 @@ static int spinand_write_to_cache_op(struct spinand_device *spinand,
 
 	wdesc = spinand->dirmaps[req->pos.plane].wdesc;
 
-	if (nand->ecc.engine->integration == NAND_ECC_ENGINE_INTEGRATION_PIPELINED &&
-	    req->mode != MTD_OPS_RAW)
+	if (nand_ecc_is_pipelined(nand) && req->mode != MTD_OPS_RAW)
 		wdesc->info.op_tmpl->data.ecc = true;
 	else
 		wdesc->info.op_tmpl->data.ecc = false;
@@ -1261,7 +1259,7 @@ static int spinand_create_dirmap(struct spinand_device *spinand,
 	struct spi_mem_dirmap_desc *desc;
 	bool enable_ecc = false, secondary_op = false;
 
-	if (nand->ecc.engine->integration == NAND_ECC_ENGINE_INTEGRATION_PIPELINED)
+	if (nand_ecc_is_pipelined(nand))
 		enable_ecc = true;
 
 	if (spinand->cont_read_possible && spinand->op_templates->cont_read_cache)
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 09c8c93e4dba..6936180b6ea5 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -305,6 +305,8 @@ int nand_ecc_prepare_io_req(struct nand_device *nand,
 			    struct nand_page_io_req *req);
 int nand_ecc_finish_io_req(struct nand_device *nand,
 			   struct nand_page_io_req *req);
+bool nand_ecc_is_pipelined(const struct nand_device *nand);
+
 bool nand_ecc_is_strong_enough(struct nand_device *nand);
 
 #if IS_REACHABLE(CONFIG_MTD_NAND_CORE)

-- 
2.55.0