[PATCH] FS: nilfs2: clamps ns_r_segments_percentage to [1, 99]

[Haogang Chen <haogangchen@gmail.com>]

ns_r_segments_percentage is read from the disk. Bogus or malicious
value could cause integer overflow and potential security holes.
This patch reports error when mounting such bogus volumes.

Signed-off-by: Haogang Chen <haogangchen@gmail.com>
---
 fs/nilfs2/the_nilfs.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index d327140..e12b47b 100644
--- 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;
-- 
1.7.5.4