mtd: afs: validate v2 image info bounds

The AFS v2 parser uses footer[8] to locate the image information block
inside the current erase block, then uses the image information
region_count to walk entries from a fixed local array. The footer offset
and region count come from flash contents and are not checked against the
erase block or the local image-info array before use.

Reject v2 entries whose image information offset would underflow the
erase block calculation, and reject region counts that cannot fit in the
local image-info array before walking region entries.

Fixes: b7cf5e2830 ("mtd: afs: add v2 partition parsing")
Cc: [email protected]
Signed-off-by: Pengpeng Hou <[email protected]>
Acked-by: Linus Walleij <[email protected]>
Signed-off-by: Miquel Raynal <[email protected]>

drivers/mtd/parsers/afs.c

@@ -235,6 +235,9 @@ static int afs_parse_v2_partition(struct mtd_info *mtd,
 	pr_debug("Parsing v2 partition @%08x-%08x\n",
 		 off, off + mtd->erasesize);
 
+	if (mtd->erasesize < sizeof(footer))
+		return -EINVAL;
+
 	/* First read the footer */
 	ptr = off + mtd->erasesize - sizeof(footer);
 	ret = mtd_read(mtd, ptr, sizeof(footer), &sz, (u_char *)footer);
@@ -245,6 +248,8 @@ static int afs_parse_v2_partition(struct mtd_info *mtd,
 	}
 	name = (char *) &footer[0];
 	version = footer[9];
+	if (footer[8] > mtd->erasesize - sizeof(footer))
+		return -EINVAL;
 	ptr = off + mtd->erasesize - sizeof(footer) - footer[8];
 
 	pr_debug("found image \"%s\", version %08x, info @%08x\n",
@@ -278,6 +283,8 @@ static int afs_parse_v2_partition(struct mtd_info *mtd,
 	entrypoint = imginfo[pad];
 	attributes = imginfo[pad+1];
 	region_count = imginfo[pad+2];
+	if (region_count > (ARRAY_SIZE(imginfo) - pad - 3) / 4)
+		return -EINVAL;
 	block_start = imginfo[20];
 	block_end = imginfo[21];