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 ad9fd08f66bab91aed41c7b4deca9824d4cc9173..44a1f356aca295c5e926e3f0bfcc3fae2446c1a2 100644 (file)
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1088,9 +1088,10 @@ 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;
        }
@@ -1100,6 +1101,13 @@ 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,