Intermediate value of fat_clusters can be overflowed on 32bits arch.
Reported-by: Krzysztof Strasburger <stras...@chkw386.ch.pwr.wroc.pl>
Signed-off-by: OGAWA Hirofumi <hirof...@mail.parknet.co.jp>
---
fs/fat/inode.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff -puN fs/fat/inode.c~fat-fat_clusters-overflow-fix fs/fat/inode.c
--- linux/fs/fat/inode.c~fat-fat_clusters-overflow-fix 2013-05-01
09:37:27.000000000 +0900
+++ linux-hirofumi/fs/fat/inode.c 2013-05-01 09:43:13.000000000 +0900
@@ -1223,6 +1223,19 @@ static int fat_read_root(struct inode *i
return 0;
}
+static unsigned long calc_fat_clusters(struct super_block *sb)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+ /* Divide first to avoid overflow */
+ if (sbi->fat_bits != 12) {
+ unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits;
+ return ent_per_sec * sbi->fat_length;
+ }
+
+ return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
+}
+
/*
* Read the super block of an MS-DOS FS.
*/
@@ -1427,7 +1440,7 @@ int fat_fill_super(struct super_block *s
sbi->dirty = b->fat16.state & FAT_STATE_DIRTY;
/* check that FAT table does not overflow */
- fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
+ fat_clusters = calc_fat_clusters(sb);
total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
if (total_clusters > MAX_FAT(sb)) {
if (!silent)
_
--
OGAWA Hirofumi <hirof...@mail.parknet.co.jp>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
