[PATCH 1/2] mtd: spi-nor: Fix shift-out-of-bounds

[Tudor Ambarus]

When paring SFDP we may choose to mask out an erase type, passing
an erase size of zero to spi_nor_set_erase_type().
Fix shift-out-of-bounds and just clear the erase params when
passing zero for erase size.
While here avoid a superfluous dereference and use 'size' directly.

UBSAN: shift-out-of-bounds in drivers/mtd/spi-nor/core.c:2237:24
shift exponent 4294967295 is too large for 32-bit type 'int'

Fixes: 5390a8df769e ("mtd: spi-nor: add support to non-uniform SFDP SPI NOR flash memories")
Reported-by: Alexander Stein <Alexander.Stein@xxxxxxxxxxxx>
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
---
 drivers/mtd/spi-nor/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 3d97c189c332..a1b5d5432f41 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2230,8 +2230,13 @@ void spi_nor_set_erase_type(struct spi_nor_erase_type *erase, u32 size,
 	erase->size = size;
 	erase->opcode = opcode;
 	/* JEDEC JESD216B Standard imposes erase sizes to be power of 2. */
-	erase->size_shift = ffs(erase->size) - 1;
-	erase->size_mask = (1 << erase->size_shift) - 1;
+	if (size) {
+		erase->size_shift = ffs(size) - 1;
+		erase->size_mask = (1 << erase->size_shift) - 1;
+	} else {
+		erase->size_shift = 0;
+		erase->size_mask = 0;
+	}
 }
 
 /**
-- 
2.25.1