The original code did not check for size of device. A truncated device
would mount, I/O failures would occur when "attempt to access beyond end
of device", leading to data lost.
Fix this by comparing total-sectors field in BPB with size of device.
This commit also prints a KERN_INFO message if there are extra sectors
at end of device (ie. total sectors < device sectors).
Signed-off-by: Zheng Lv <lv.zheng.2015@xxxxxxxxx>
---
fs/fat/inode.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 3bcf579..211f7bb 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1583,6 +1583,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
struct msdos_sb_info *sbi;
u16 logical_sector_size;
u32 total_sectors, total_clusters, fat_clusters, rootdir_sectors;
+ u64 device_sectors;
int debug;
long error;
char buf[50];
@@ -1738,6 +1739,17 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
if (total_sectors == 0)
total_sectors = bpb.fat_total_sect;
+ device_sectors = sb->s_bdev->bd_inode->i_size / logical_sector_size;
+ if (device_sectors && total_sectors > device_sectors) {
+ fat_msg(sb, KERN_ERR, "total sectors %u "
+ "exceeds size of device (%llu sectors)",
+ total_sectors, device_sectors);
+ goto out_invalid;
+ } else if (device_sectors && total_sectors < device_sectors) {
+ fat_msg(sb, KERN_INFO, "%llu unused sectors at end of device",
+ device_sectors - total_sectors);
+ }
+
total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
if (sbi->fat_bits != 32)
--
2.7.4
--
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