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Re: [PATCH] libxfs: don't write uninitialized heap contents into new dir

To: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Subject: Re: [PATCH] libxfs: don't write uninitialized heap contents into new directory blocks
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Thu, 19 Mar 2015 14:28:34 -0400
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20150318232159.GA24608@xxxxxxxxxxxxxxxx>
References: <20150318232159.GA24608@xxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Wed, Mar 18, 2015 at 04:21:59PM -0700, Darrick J. Wong wrote:
> When we're initializing a new directory block, zero the buffer
> contents to avoid writing random heap contents (and crc thereof)
> to disk.  This eliminates a few valgrind complaints in xfs_repair.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---

Well it seems Ok to me:

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

... but I do notice that we start ending up with multiple memset() calls
throughout these codepaths. E.g., xfs_dir3_data_init() memsets the
target bytes for the header if crc is enabled, xfs_dir3_leaf_get_buf()
calls xfs_dir3_leaf_init() which does something similar, etc.

I wonder if we should just zero the buffer content unconditionally on
allocation?

Brian

>  libxfs/xfs_da_btree.c  |    1 +
>  libxfs/xfs_dir2_data.c |    1 +
>  libxfs/xfs_dir2_leaf.c |    1 +
>  libxfs/xfs_dir2_node.c |    2 +-
>  4 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/libxfs/xfs_da_btree.c b/libxfs/xfs_da_btree.c
> index b731b54..bc73cbc 100644
> --- a/libxfs/xfs_da_btree.c
> +++ b/libxfs/xfs_da_btree.c
> @@ -562,6 +562,7 @@ xfs_da3_root_split(
>       if (error)
>               return error;
>       node = bp->b_addr;
> +     memset(bp->b_addr, 0, bp->b_bcount);
>       oldroot = blk1->bp->b_addr;
>       if (oldroot->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC) ||
>           oldroot->hdr.info.magic == cpu_to_be16(XFS_DA3_NODE_MAGIC)) {
> diff --git a/libxfs/xfs_dir2_data.c b/libxfs/xfs_dir2_data.c
> index dc9df4d..79c2fc2 100644
> --- a/libxfs/xfs_dir2_data.c
> +++ b/libxfs/xfs_dir2_data.c
> @@ -559,6 +559,7 @@ xfs_dir3_data_init(
>               XFS_DATA_FORK);
>       if (error)
>               return error;
> +     memset(bp->b_addr, 0, bp->b_bcount);
>       bp->b_ops = &xfs_dir3_data_buf_ops;
>       xfs_trans_buf_set_type(tp, bp, XFS_BLFT_DIR_DATA_BUF);
>  
> diff --git a/libxfs/xfs_dir2_leaf.c b/libxfs/xfs_dir2_leaf.c
> index 8e0cbc9..6eb03fc 100644
> --- a/libxfs/xfs_dir2_leaf.c
> +++ b/libxfs/xfs_dir2_leaf.c
> @@ -382,6 +382,7 @@ xfs_dir3_leaf_get_buf(
>       if (error)
>               return error;
>  
> +     memset(bp->b_addr, 0, bp->b_bcount);
>       xfs_dir3_leaf_init(mp, tp, bp, dp->i_ino, magic);
>       xfs_dir3_leaf_log_header(tp, bp);
>       if (magic == XFS_DIR2_LEAF1_MAGIC)
> diff --git a/libxfs/xfs_dir2_node.c b/libxfs/xfs_dir2_node.c
> index 3737e4e..3e2f04d 100644
> --- a/libxfs/xfs_dir2_node.c
> +++ b/libxfs/xfs_dir2_node.c
> @@ -247,7 +247,7 @@ xfs_dir3_free_get_buf(
>        * Initialize the new block to be empty, and remember
>        * its first slot as our empty slot.
>        */
> -     memset(bp->b_addr, 0, sizeof(struct xfs_dir3_free_hdr));
> +     memset(bp->b_addr, 0, bp->b_bcount);
>       memset(&hdr, 0, sizeof(hdr));
>  
>       if (xfs_sb_version_hascrc(&mp->m_sb)) {
> 
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