From cd80a4fe611d7cb4153a6ed39d1e5052c702fb12 Mon Sep 17 00:00:00 2001
From: Patrick Wildt <patrick@blueri.se>
Date: Mon, 26 Nov 2018 15:56:57 +0100
Subject: [PATCH] fs: check FAT cluster size
The cluster size specifies how many sectors make up a cluster. A
cluster size of zero makes no sense, as it would mean that the
cluster is made up of no sectors. This will later lead into a
division by zero in sect_to_clust(), so better take care of that
early.
The MAX_CLUSTSIZE define can reduced using a define to make some
room in low-memory system. Unfortunately if the code reads a
filesystem with a bigger cluster size it will overflow the buffer.
Signed-off-by: Patrick Wildt <patrick@blueri.se>
---
fs/fat/fat.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 4bc3030ab8..e0c076763f 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -571,6 +571,17 @@ static int get_fs_info(fsdata *mydata)
mydata->sect_size, cur_part_info.blksz);
return -1;
}
+ if (mydata->clust_size == 0) {
+ printf("Error: FAT cluster size not set\n");
+ return -1;
+ }
+ if ((unsigned int)mydata->clust_size * mydata->sect_size >
+ MAX_CLUSTSIZE) {
+ printf("Error: FAT cluster size too big (cs=%u, max=%u)\n",
+ (unsigned int)mydata->clust_size * mydata->sect_size,
+ MAX_CLUSTSIZE);
+ return -1;
+ }
if (mydata->fatsize == 32) {
mydata->data_begin = mydata->rootdir_sect -
--
2.39.5