diff options
author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2013-05-24 18:55:08 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-24 19:22:50 -0400 |
commit | 7b92d03c3239f43e5b86c9cc9630f026d36ee995 (patch) | |
tree | 230d35077a9c99203a86a7abc94ce8d6645e23fb /fs | |
parent | 5eeb929390de7d5219483a1ca10cce4a84066099 (diff) |
fat: fix possible overflow for fat_clusters
Intermediate value of fat_clusters can be overflowed on 32bits arch.
Reported-by: Krzysztof Strasburger <strasbur@chkw386.ch.pwr.wroc.pl>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/fat/inode.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/fs/fat/inode.c b/fs/fat/inode.c index dfce656ddb33..5d4513cb1b3c 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c | |||
@@ -1229,6 +1229,19 @@ static int fat_read_root(struct inode *inode) | |||
1229 | return 0; | 1229 | return 0; |
1230 | } | 1230 | } |
1231 | 1231 | ||
1232 | static unsigned long calc_fat_clusters(struct super_block *sb) | ||
1233 | { | ||
1234 | struct msdos_sb_info *sbi = MSDOS_SB(sb); | ||
1235 | |||
1236 | /* Divide first to avoid overflow */ | ||
1237 | if (sbi->fat_bits != 12) { | ||
1238 | unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits; | ||
1239 | return ent_per_sec * sbi->fat_length; | ||
1240 | } | ||
1241 | |||
1242 | return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits; | ||
1243 | } | ||
1244 | |||
1232 | /* | 1245 | /* |
1233 | * Read the super block of an MS-DOS FS. | 1246 | * Read the super block of an MS-DOS FS. |
1234 | */ | 1247 | */ |
@@ -1434,7 +1447,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, | |||
1434 | sbi->dirty = b->fat16.state & FAT_STATE_DIRTY; | 1447 | sbi->dirty = b->fat16.state & FAT_STATE_DIRTY; |
1435 | 1448 | ||
1436 | /* check that FAT table does not overflow */ | 1449 | /* check that FAT table does not overflow */ |
1437 | fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits; | 1450 | fat_clusters = calc_fat_clusters(sb); |
1438 | total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT); | 1451 | total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT); |
1439 | if (total_clusters > MAX_FAT(sb)) { | 1452 | if (total_clusters > MAX_FAT(sb)) { |
1440 | if (!silent) | 1453 | if (!silent) |