linux-kernel - Re: [PATCH] btrfs: Fix incorrect check causing NULL pointer derefernce

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Message-ID: <20191216161639.GD3929@twin.jikos.cz>
Date:   Mon, 16 Dec 2019 17:16:39 +0100
From:   David Sterba <dsterba@...e.cz>
To:     Aditya Pakki <pakki001@....edu>
Cc:     kjlu@....edu, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: Fix incorrect check causing NULL pointer
 derefernce

On Sun, Dec 15, 2019 at 11:32:26AM -0600, Aditya Pakki wrote:
> In btrfsic_process_superblock, argument state is dereferenced for
> the variable fs_info and then checked for NULL. The patch fixes
> this issue by returning an error if state is NULL and then assigns
> fs_info.
> 
> Signed-off-by: Aditya Pakki <pakki001@....edu>
> ---
>  fs/btrfs/check-integrity.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
> index 0b52ab4cb964..70d7a05cafad 100644
> --- a/fs/btrfs/check-integrity.c
> +++ b/fs/btrfs/check-integrity.c
> @@ -629,15 +629,18 @@ static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
>  static int btrfsic_process_superblock(struct btrfsic_state *state,
>  				      struct btrfs_fs_devices *fs_devices)
>  {
> -	struct btrfs_fs_info *fs_info = state->fs_info;
> -	struct btrfs_super_block *selected_super;
> +	struct btrfsic_dev_state *selected_dev_state = NULL;
>  	struct list_head *dev_head = &fs_devices->devices;
> +	struct btrfs_super_block *selected_super;
> +	struct btrfs_fs_info *fs_info;
>  	struct btrfs_device *device;
> -	struct btrfsic_dev_state *selected_dev_state = NULL;
>  	int ret = 0;
>  	int pass;
>  
> -	BUG_ON(NULL == state);

A fix for this has already been merged to our development queue. Thanks.