linux-kernel - Re: [PATCH v2] btrfs: fix a NULL pointer dereference

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Message-ID: <95cfa934-4677-0c7f-781e-6ce35a87f9d6@suse.com>
Date:   Thu, 14 Mar 2019 10:16:08 +0200
From:   Nikolay Borisov <nborisov@...e.com>
To:     Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....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 v2] btrfs: fix a NULL pointer dereference



On 14.03.19 г. 10:13 ч., Kangjie Lu wrote:
> btrfs_lookup_block_group may fail and return NULL. The fix uses
> assert to ensure cache is not NULL.
> 
> Signed-off-by: Kangjie Lu <kjlu@....edu>

Reviewed-by: Nikolay Borisov <nborisov@...e.com>

> 
> ---
> V2: use assert as suggested by Nikolay Borisov <nborisov@...e.com>
> ---
>  fs/btrfs/extent-tree.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 994f0cc41799..80d7c272d282 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -7303,6 +7303,7 @@ void btrfs_free_tree_block(struct btrfs_trans_handle *trans,
>  
>  		pin = 0;
>  		cache = btrfs_lookup_block_group(fs_info, buf->start);
> +		ASSERT(cache);
>  
>  		if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN)) {
>  			pin_down_extent(fs_info, cache, buf->start,
>