[PATCH 3.16 146/366] ext4: add more mount time checks of the superblock

Ben Hutchings
2018-11-11T19:49:05Z

From: Theodore Ts'o <tytso@mit.edu>

commit bfe0a5f47ada40d7984de67e59a7d3390b9b9ecc upstream.

The kernel's ext4 mount-time checks were more permissive than
e2fsprogs's libext2fs checks when opening a file system. The
superblock is considered too insane for debugfs or e2fsck to operate
on it, the kernel has no business trying to mount it.

This will make file system fuzzing tools work harder, but the failure
cases that they find will be more useful and be easier to evaluate.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext4/super.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3725,6 +3725,13 @@ static int ext4_fill_super(struct super_
le32_to_cpu(es->s_log_block_size));
goto failed_mount;
}
+ if (le32_to_cpu(es->s_log_cluster_size) >
+ (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
+ ext4_msg(sb, KERN_ERR,
+ "Invalid log cluster size: %u",
+ le32_to_cpu(es->s_log_cluster_size));
+ goto failed_mount;
+ }

if (le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) > (blocksize / 4)) {
ext4_msg(sb, KERN_ERR,
@@ -3853,13 +3860,6 @@ static int ext4_fill_super(struct super_
"block size (%d)", clustersize, blocksize);
goto failed_mount;
}
- if (le32_to_cpu(es->s_log_cluster_size) >
- (EXT4_MAX_CLUSTER_LOG_SIZE - EXT4_MIN_BLOCK_LOG_SIZE)) {
- ext4_msg(sb, KERN_ERR,
- "Invalid log cluster size: %u",
- le32_to_cpu(es->s_log_cluster_size));
- goto failed_mount;
- }
sbi->s_cluster_bits = le32_to_cpu(es->s_log_cluster_size) -
le32_to_cpu(es->s_log_block_size);
sbi->s_clusters_per_group =
@@ -3880,10 +3880,10 @@ static int ext4_fill_super(struct super_
}
} else {
if (clustersize != blocksize) {
- ext4_warning(sb, "fragment/cluster size (%d) != "
- "block size (%d)", clustersize,
- blocksize);
- clustersize = blocksize;
+ ext4_msg(sb, KERN_ERR,
+ "fragment/cluster size (%d) != "
+ "block size (%d)", clustersize, blocksize);
+ goto failed_mount;
}
if (sbi->s_blocks_per_group > blocksize * 8) {
ext4_msg(sb, KERN_ERR,
@@ -3937,6 +3937,13 @@ static int ext4_fill_super(struct super_
ext4_blocks_count(es));
goto failed_mount;
}
+ if ((es->s_first_data_block == 0) && (es->s_log_block_size == 0) &&
+ (sbi->s_cluster_ratio == 1)) {
+ ext4_msg(sb, KERN_WARNING, "bad geometry: first data "
+ "block is 0 with a 1k block and cluster size");
+ goto failed_mount;
+ }
+
blocks_count = (ext4_blocks_count(es) -
le32_to_cpu(es->s_first_data_block) +
EXT4_BLOCKS_PER_GROUP(sb) - 1);
@@ -3972,6 +3979,14 @@ static int ext4_fill_super(struct super_
ret = -ENOMEM;
goto failed_mount;
}
+ if (((u64)sbi->s_groups_count * sbi->s_inodes_per_group) !=
+ le32_to_cpu(es->s_inodes_count)) {
+ ext4_msg(sb, KERN_ERR, "inodes count not valid: %u vs %llu",
+ le32_to_cpu(es->s_inodes_count),
+ ((u64)sbi->s_groups_count * sbi->s_inodes_per_group));
+ ret = -EINVAL;
+ goto failed_mount;
+ }

if (ext4_proc_root)
sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root);