[PATCH] mtd: spi-nor: sfdp: reduce stack usage in spi_nor_parse_sfdp()

[PATCH] mtd: spi-nor: sfdp: reduce stack usage in spi_nor_parse_sfdp()

[Michael Walle]

Two large spi_nor_flash_parameter structures on a function stack
are really too much, and this can exceed an otherwise reasonable
frame limit:

drivers/mtd/spi-nor/sfdp.c: In function 'spi_nor_parse_sfdp':
drivers/mtd/spi-nor/sfdp.c:1717:1: error: the frame size of 1600 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]

Allocate both rollback copies on the heap and use structure copies
for type safety.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: David Laight <david.laight.linux@gmail.com>
Fixes: d20029474a76 ("mtd: spi-nor: push the rollback mechanism into the sfdp module")
Signed-off-by: Michael Walle <mwalle@kernel.org>
---
 drivers/mtd/spi-nor/sfdp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index beb0f5c66212..e30cdb5b18ed 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -1535,9 +1535,9 @@ int spi_nor_check_sfdp_signature(struct spi_nor *nor)
  */
 int spi_nor_parse_sfdp(struct spi_nor *nor)
 {
+	struct spi_nor_flash_parameter *save_params __free(kfree) = kmalloc_objs(*save_params, 2);
 	const struct sfdp_parameter_header *param_header, *bfpt_header;
 	struct sfdp_parameter_header *param_headers = NULL;
-	struct spi_nor_flash_parameter params, params2;
 	struct sfdp_header header;
 	struct device *dev = nor->dev;
 	struct sfdp *sfdp;
@@ -1549,7 +1549,9 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 	 * Get a backup of all the parameter to roll back to in case of an
 	 * error.
 	 */
-	memcpy(&params, nor->params, sizeof(params));
+	if (!save_params)
+		return -ENOMEM;
+	save_params[0] = *nor->params;
 
 	/* Get the SFDP header. */
 	err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sizeof(header), &header);
@@ -1665,7 +1667,7 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 
 	/* Parse optional parameter tables. */
 	for (i = 0; i < header.nph; i++) {
-		memcpy(&params2, nor->params, sizeof(params2));
+		save_params[1] = *nor->params;
 		param_header = &param_headers[i];
 
 		switch (SFDP_PARAM_HEADER_ID(param_header)) {
@@ -1703,7 +1705,7 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 			 * spi_nor_flash_parameter data.
 			 */
 			err = 0;
-			memcpy(nor->params, &params2, sizeof(*nor->params));
+			*nor->params = save_params[1];
 		}
 	}
 
@@ -1724,7 +1726,7 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 free_param_headers:
 	kfree(param_headers);
 	if (err)
-		memcpy(nor->params, &params, sizeof(*nor->params));
+		*nor->params = save_params[0];
 
 	return err;
 }
-- 
2.47.3

Re: [PATCH] mtd: spi-nor: sfdp: reduce stack usage in spi_nor_parse_sfdp()

[Miquel Raynal]

On 15/10/2026 at 11:01:28 +02, Michael Walle <mwalle@kernel.org> wrote:

> Two large spi_nor_flash_parameter structures on a function stack
> are really too much, and this can exceed an otherwise reasonable
> frame limit:
>
> drivers/mtd/spi-nor/sfdp.c: In function 'spi_nor_parse_sfdp':
> drivers/mtd/spi-nor/sfdp.c:1717:1: error: the frame size of 1600 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
>
> Allocate both rollback copies on the heap and use structure copies
> for type safety.
>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Suggested-by: David Laight <david.laight.linux@gmail.com>
> Fixes: d20029474a76 ("mtd: spi-nor: push the rollback mechanism into the sfdp module")
> Signed-off-by: Michael Walle <mwalle@kernel.org>

Sashiko is correct about the need for not mixing __free and goto's. With
this fixed,

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>