3.2.46-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: OGAWA Hirofumi <hirof...@mail.parknet.co.jp>
commit 7b92d03c3239f43e5b86c9cc9630f026d36ee995 upstream.
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>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
fs/fat/inode.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1238,6 +1238,19 @@ 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.
*/
@@ -1434,7 +1447,7 @@ int fat_fill_super(struct super_block *s
sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
/* 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)
--
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