nilfs2: clamp ns_r_segments_percentage to [1, 99]

ns_r_segments_percentage is read from the disk.  Bogus or malicious
value could cause integer overflow and malfunction due to meaningless
disk usage calculation.  This patch reports error when mounting such
bogus volumes.

Signed-off-by: Haogang Chen <haogangchen@gmail.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index d327140..8a75901 100644 (file)
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -409,6 +409,12 @@ static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
        nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);
        nilfs->ns_r_segments_percentage =
                le32_to_cpu(sbp->s_r_segments_percentage);
+       if (nilfs->ns_r_segments_percentage < 1 ||
+           nilfs->ns_r_segments_percentage > 99) {
+               printk(KERN_ERR "NILFS: invalid reserved segments percentage.\n");
+               return -EINVAL;
+       }
+
        nilfs_set_nsegments(nilfs, le64_to_cpu(sbp->s_nsegments));
        nilfs->ns_crc_seed = le32_to_cpu(sbp->s_crc_seed);
        return 0;