linux-ext4 - Re: [PATCH] ext2: Fix memory leak when truncate races ext2_get

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Date:   Thu, 13 Jul 2017 13:46:31 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ernesto A. Fernández 
        <ernesto.mnd.fernandez@...il.com>
Cc:     jack@...e.com, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext2: Fix memory leak when truncate races ext2_get_blocks

On Fri 23-06-17 21:37:21, Ernesto A. Fernández wrote:
> Buffer heads referencing indirect blocks may not be released if the file
> is truncated at the right time. This happens because ext2_get_branch()
> returns NULL when it finds the whole chain of indirect blocks already
> set, and when truncate alters the chain this value of NULL is
> treated as the address of the last head to be released. Handle this in the
> same way as it's done after the got_it label.
> 
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com>
> ---
> Despite trying I haven't actually managed to trigger this race. I tested
> the patch by inducing regular failures in verify_chain().

Thanks! I've merged the patch to my tree.

								Honza

> 
>  fs/ext2/inode.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
> index 2dcbd56..30163d0 100644
> --- a/fs/ext2/inode.c
> +++ b/fs/ext2/inode.c
> @@ -659,6 +659,7 @@ static int ext2_get_blocks(struct inode *inode,
>  				 */
>  				err = -EAGAIN;
>  				count = 0;
> +				partial = chain + depth - 1;
>  				break;
>  			}
>  			blk = le32_to_cpu(*(chain[depth-1].p + count));
> -- 
> 2.1.4
> 
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR