3.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: OGAWA Hirofumi <[email protected]> commit 7b92d03c3239f43e5b86c9cc9630f026d36ee995 upstream. Intermediate value of fat_clusters can be overflowed on 32bits arch. Reported-by: Krzysztof Strasburger <[email protected]> Signed-off-by: OGAWA Hirofumi <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/fat/inode.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
