ext2: Add more validity checks for inode counts

[ Upstream commit fa78f336937240d1bc598db817d638086060e7e9 ]

Add checks verifying number of inodes stored in the superblock matches
the number computed from number of inodes per group. Also verify we have
at least one block worth of inodes per group. This prevents crashes on
corrupted filesystems.

Reported-by: syzbot+d273f7d7f58afd93be48@syzkaller.appspotmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 3d21279fe2cb5e27e1cb08c1b66d6929786eff8a..fd855574ef0928cb809319579c93fc9e783747fa 100644 (file)
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1058,9 +1058,10 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
                        sbi->s_frags_per_group);
                goto failed_mount;
        }
-       if (sbi->s_inodes_per_group > sb->s_blocksize * 8) {
+       if (sbi->s_inodes_per_group < sbi->s_inodes_per_block ||
+           sbi->s_inodes_per_group > sb->s_blocksize * 8) {
                ext2_msg(sb, KERN_ERR,
-                       "error: #inodes per group too big: %lu",
+                       "error: invalid #inodes per group: %lu",
                        sbi->s_inodes_per_group);
                goto failed_mount;
        }
@@ -1070,6 +1071,13 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
        sbi->s_groups_count = ((le32_to_cpu(es->s_blocks_count) -
                                le32_to_cpu(es->s_first_data_block) - 1)
                                        / EXT2_BLOCKS_PER_GROUP(sb)) + 1;
+       if ((u64)sbi->s_groups_count * sbi->s_inodes_per_group !=
+           le32_to_cpu(es->s_inodes_count)) {
+               ext2_msg(sb, KERN_ERR, "error: invalid #inodes: %u vs computed %llu",
+                        le32_to_cpu(es->s_inodes_count),
+                        (u64)sbi->s_groups_count * sbi->s_inodes_per_group);
+               goto failed_mount;
+       }
        db_count = (sbi->s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
                   EXT2_DESC_PER_BLOCK(sb);
        sbi->s_group_desc = kmalloc_array(db_count,