Re: [PATCH 2/7] ext4: possible sbi->s_group_desc leak in ext4_fill_super

[Theodore Y. Ts'o]

On Wed, Oct 31, 2018 at 10:12:27PM +0300, Vasily Averin wrote:
> Fixes bfe0a5f47ada ("ext4: add more mount time checks of the superblock") # 
> 4.18
> 
> Signed-off-by: Vasily Averin <v...@virtuozzo.com>
> ---
>  fs/ext4/super.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index a221f1cdf704..ed4d36506ec2 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4100,7 +4100,8 @@ static int ext4_fill_super(struct super_block *sb, void 
> *data, int silent)
>                        le32_to_cpu(es->s_inodes_count),
>                        ((u64)sbi->s_groups_count * sbi->s_inodes_per_group));
>               ret = -EINVAL;
> -             goto failed_mount;
> +             db_count = 0;
> +             goto failed_mount2;
>       }
>  
>       bgl_lock_init(sbi->s_blockgroup_lock);

Thanks for spotting this!

A better fix would be to move this check earlier, before the
allocation of sbi->s_group_desc.

                                                - Ted

commit 9fa8bc9b9d3c6864f8dddd83893a02fcc1b48b62
Author: Theodore Ts'o <ty...@mit.edu>
Date:   Wed Nov 7 10:32:53 2018 -0500

    ext4: fix possible leak of sbi->s_group_desc_leak in error path
    
    Fixes: bfe0a5f47ada ("ext4: add more mount time checks of the superblock")
    Reported-by: Vasily Averin <v...@virtuozzo.com>
    Signed-off-by: Theodore Ts'o <ty...@mit.edu>
    Cc: sta...@kernel.org # 4.18

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a221f1cdf704..92092b55db1e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4075,6 +4075,14 @@ static int ext4_fill_super(struct super_block *sb, void 
*data, int silent)
        sbi->s_groups_count = blocks_count;
        sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
                        (EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));
+       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;
+       }
        db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
                   EXT4_DESC_PER_BLOCK(sb);
        if (ext4_has_feature_meta_bg(sb)) {
@@ -4094,14 +4102,6 @@ static int ext4_fill_super(struct super_block *sb, void 
*data, int silent)
                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;
-       }
 
        bgl_lock_init(sbi->s_blockgroup_lock);