[PATCH v3 4/5] mtd: rawnand: brcmnand: Fix potential out-of-bounds access in oob write

[William Zhang]

When the oob buffer length is not in multiple of words, the oob write
function does out-of-bounds read on the oob source buffer at the last
iteration. Fix that by always checking length limit on the oob buffer
read and fill with 0xff when reaching the end of the buffer to the oob
registers.

Fixes: 27c5b17cd1b1 ("mtd: nand: add NAND driver "library" for Broadcom STB NAND controller")
Signed-off-by: William Zhang <william.zhang at broadcom.com>
Reviewed-by: Florian Fainelli <florian.fainelli at broadcom.com>

---

Changes in v3:
- Fix kernel test robot sparse warning:
   drivers/mtd/nand/raw/brcmnand/brcmnand.c:1500:54: sparse: expected unsigned int [usertype] data
   drivers/mtd/nand/raw/brcmnand/brcmnand.c:1500:54: sparse: got restricted __be32 [usertype]

Changes in v2:
- Handle the remaining unaligned oob data after the oob data write loop

 drivers/mtd/nand/raw/brcmnand/brcmnand.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
index ea03104692bf..407bf79cbaf4 100644
--- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
@@ -1477,19 +1477,28 @@ static int write_oob_to_regs(struct brcmnand_controller *ctrl, int i,
 			     const u8 *oob, int sas, int sector_1k)
 {
 	int tbytes = sas << sector_1k;
-	int j;
+	int j, k = 0;
+	u32 last = 0xffffffff;
+	u8 *plast = (u8 *)&last;
 
 	/* Adjust OOB values for 1K sector size */
 	if (sector_1k && (i & 0x01))
 		tbytes = max(0, tbytes - (int)ctrl->max_oob);
 	tbytes = min_t(int, tbytes, ctrl->max_oob);
 
-	for (j = 0; j < tbytes; j += 4)
+	for (j = 0; (j + 3) < tbytes; j += 4)
 		oob_reg_write(ctrl, j,
 				(oob[j + 0] << 24) |
 				(oob[j + 1] << 16) |
 				(oob[j + 2] <<  8) |
 				(oob[j + 3] <<  0));
+
+	while (j < tbytes)
+		plast[k++] = oob[j++];
+
+	if (tbytes & 0x3)
+		oob_reg_write(ctrl, (tbytes & ~0x3), (__force u32)cpu_to_be32(last));
+
 	return tbytes;
 }
 
-- 
2.37.3

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