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| author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2013-05-24 15:55:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-24 16:22:50 -0700 |
| commit | 7b92d03c3239f43e5b86c9cc9630f026d36ee995 (patch) | |
| tree | 230d35077a9c99203a86a7abc94ce8d6645e23fb /fs/fat/inode.c | |
| parent | 5eeb929390de7d5219483a1ca10cce4a84066099 (diff) | |
| download | lwn-7b92d03c3239f43e5b86c9cc9630f026d36ee995.tar.gz lwn-7b92d03c3239f43e5b86c9cc9630f026d36ee995.zip | |
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/fat/inode.c')
| -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) 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 *sb, void *data, int silent, int isvfat, 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) |