Re: [PATCH] ext4: don't kfree uninitialized s_group_info members

[Ted Ts'o <tytso@mit.edu>]

On Thu, Mar 10, 2011 at 05:03:15PM -0600, Eric Sandeen wrote:
> Per kernel.org bugzilla #30872 we may call kfree on uninitialized
> members of the s_group_info array.  We can avoid this by kzalloc'ing
> the array, and only freeing them on the error path if they are
> non-zero.
> 
> This doesn't entirely solve the oops on mount if we fail down this
> path; failed_mount4: frees the sbi, for one, which gets referenced
> later in the failed mount paths - I haven't worked that out yet.
> 
> Reported-by: Eugene A. Shatokhin <dame_eugene@mail.ru>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Added to the ext4 patch tree, although I've dropped the second patch
hunk, since it's OK to call kfree on a NULL pointers:

> @@ -2412,7 +2412,8 @@ err_freebuddy:
>  		kmem_cache_free(cachep, ext4_get_group_info(sb, i));
>  	i = num_meta_group_infos;
>  	while (i-- > 0)
> -		kfree(sbi->s_group_info[i]);
> +		if (sbi->s_group_info[i])
> +			kfree(sbi->s_group_info[i]);
>  	iput(sbi->s_buddy_cache);
>  err_freesgi:
>  	kfree(sbi->s_group_info);

							- Ted