mtd: parsers: qcom: Fix kernel panic on skipped partition

In the event of a skipped partition (case when the entry name is empty)
the kernel panics in the cleanup function as the name entry is NULL.
Rework the parser logic by first checking the real partition number and
then allocate the space and set the data for the valid partitions.

The logic was also fundamentally wrong as with a skipped partition, the
parts number returned was incorrect by not decreasing it for the skipped
partitions.

Fixes: 803eb12 ("mtd: parsers: Add Qcom SMEM parser")
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220116032211.9728-1-ansuelsmth@gmail.com

Author: Ansuel

drivers/mtd/parsers/qcomsmempart.c

@@ -58,11 +58,11 @@ static int parse_qcomsmem_part(struct mtd_info *mtd,
 			       const struct mtd_partition **pparts,
 			       struct mtd_part_parser_data *data)
 {
+	size_t len = SMEM_FLASH_PTABLE_HDR_LEN;
+	int ret, i, j, tmpparts, numparts = 0;
 	struct smem_flash_pentry *pentry;
 	struct smem_flash_ptable *ptable;
-	size_t len = SMEM_FLASH_PTABLE_HDR_LEN;
 	struct mtd_partition *parts;
-	int ret, i, numparts;
 	char *name, *c;
 
 	if (IS_ENABLED(CONFIG_MTD_SPI_NOR_USE_4K_SECTORS)
@@ -88,8 +88,8 @@ static int parse_qcomsmem_part(struct mtd_info *mtd,
 	}
 
 	/* Ensure that # of partitions is less than the max we have allocated */
-	numparts = le32_to_cpu(ptable->numparts);
-	if (numparts > SMEM_FLASH_PTABLE_MAX_PARTS_V4) {
+	tmpparts = le32_to_cpu(ptable->numparts);
+	if (tmpparts > SMEM_FLASH_PTABLE_MAX_PARTS_V4) {
 		pr_err("Partition numbers exceed the max limit\n");
 		return -EINVAL;
 	}
@@ -117,11 +117,17 @@ static int parse_qcomsmem_part(struct mtd_info *mtd,
 		return PTR_ERR(ptable);
 	}
 
+	for (i = 0; i < tmpparts; i++) {
+		pentry = &ptable->pentry[i];
+		if (pentry->name[0] != '\0')
+			numparts++;
+	}
+
 	parts = kcalloc(numparts, sizeof(*parts), GFP_KERNEL);
 	if (!parts)
 		return -ENOMEM;
 
-	for (i = 0; i < numparts; i++) {
+	for (i = 0, j = 0; i < tmpparts; i++) {
 		pentry = &ptable->pentry[i];
 		if (pentry->name[0] == '\0')
 			continue;
@@ -136,24 +142,25 @@ static int parse_qcomsmem_part(struct mtd_info *mtd,
 		for (c = name; *c != '\0'; c++)
 			*c = tolower(*c);
 
-		parts[i].name = name;
-		parts[i].offset = le32_to_cpu(pentry->offset) * mtd->erasesize;
-		parts[i].mask_flags = pentry->attr;
-		parts[i].size = le32_to_cpu(pentry->length) * mtd->erasesize;
+		parts[j].name = name;
+		parts[j].offset = le32_to_cpu(pentry->offset) * mtd->erasesize;
+		parts[j].mask_flags = pentry->attr;
+		parts[j].size = le32_to_cpu(pentry->length) * mtd->erasesize;
 		pr_debug("%d: %s offs=0x%08x size=0x%08x attr:0x%08x\n",
 			 i, pentry->name, le32_to_cpu(pentry->offset),
 			 le32_to_cpu(pentry->length), pentry->attr);
+		j++;
 	}
 
 	pr_debug("SMEM partition table found: ver: %d len: %d\n",
-		 le32_to_cpu(ptable->version), numparts);
+		 le32_to_cpu(ptable->version), tmpparts);
 	*pparts = parts;
 
 	return numparts;
 
 out_free_parts:
-	while (--i >= 0)
-		kfree(parts[i].name);
+	while (--j >= 0)
+		kfree(parts[j].name);
 	kfree(parts);
 	*pparts = NULL;