Re: [RFC PATCH] db: Stop core dumping on attr3 if block header is not recognized

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, Apr 18, 2018 at 11:49:35AM +0200, Carlos Maiolino wrote:
> Hi,
> 
> this is supposed to fix the issue while trying to print a non attr3
> block using attr3 type, which ends up on an ASSERT, and crashing xfs_db.
> 
> This is based on Eric's suggestion, which an attempt to print the
> possible magic number from the current block.
> 
> As Eric mentioned, there are other types which need such handling too,
> but, this is supposed to be a RFC to get comments on the approach. Once
> we agree how to fix it, I'll fix the remaining types accordingly.

I'm assuming you mean attr, dir, and dir3?

> This is the following output of an attempt to print a non attr3 type block,
> with this patch:
> 
> xfs_db> fsblock 2
> xfs_db> type attr3
> Unknown attribute buffer type!
> Unknown attribute buffer type!
> xfs_db> p
> Unrecognized attr3 block, possible magic number:
> Unrecognized attr3 block, possible magic number:
> hdr.magic = 0x41423343
> 
> While, printing a correct attr3 block, nothing is changed:
> 
> xfs_db> fsblock 11
> xfs_db> type attr3
> xfs_db> p
> hdr.info.hdr.forw = 0
> hdr.info.hdr.back = 0
> hdr.info.hdr.magic = 0x3ebe
> hdr.info.crc = 0x6f7911f7 (correct)
> hdr.info.bno = 88
> .
> .
> .
> 
> Comments?
> 
> Cheers
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> ---
>  db/attr.c  | 22 ++++++++++++++++++++++
>  db/attr.h  |  1 +
>  db/field.c |  2 ++
>  db/field.h |  1 +
>  4 files changed, 26 insertions(+)
> 
> diff --git a/db/attr.c b/db/attr.c
> index 9cbb20d3..b7692e9e 100644
> --- a/db/attr.c
> +++ b/db/attr.c
> @@ -523,6 +523,21 @@ attr3_remote_hdr_count(
>  	return be32_to_cpu(node->rm_magic) == XFS_ATTR3_RMT_MAGIC;
>  }
>  
> +static int
> +attr3_unkown_hdr_count(
> +	void			*obj,
> +	int			startoff)
> +{
> +	if (!attr3_leaf_hdr_count(obj, startoff) &&
> +	    !attr3_node_hdr_count(obj, startoff) &&
> +	    !attr3_remote_hdr_count(obj,startoff)) {
> +		dbprintf(_("Unrecognized attr3 block, possible magic number:\n"));
> +		return 1;
> +	}
> +
> +	return 0;
> +}
> +
>  int
>  attr_size(
>  	void	*obj,
> @@ -549,6 +564,8 @@ const field_t	attr3_flds[] = {
>  	  FLD_COUNT, TYP_NONE },
>  	{ "hdr", FLDT_ATTR3_REMOTE_HDR, OI(0), attr3_remote_hdr_count,
>  	  FLD_COUNT, TYP_NONE },
> +	{ "hdr", FLDT_ATTR3_UNKOWN_HDR, OI(0), attr3_unkown_hdr_count,

"FLDT_ATTR3_UNKNOWN_HDR" (need extra 'N') here and elsewhere.

> +	  FLD_COUNT, TYP_NONE },
>  	{ "data", FLDT_CHARNS, OI(bitize(sizeof(struct xfs_attr3_rmt_hdr))),
>  	  attr3_remote_data_count, FLD_COUNT, TYP_NONE },
>  	{ "entries", FLDT_ATTR_LEAF_ENTRY, OI(L3OFF(entries)),
> @@ -606,6 +623,11 @@ const struct field	attr3_remote_crc_flds[] = {
>  	{ NULL }
>  };
>  
> +const struct field	attr3_unkown_flds[] = {
> +	{ "magic", FLDT_UINT32X, 0, C1, 0, TYP_NONE},

There are two possible magics for attr3 blocks -- this one, which is for
remote attr value blocks, and the xfs_da3_blkinfo magic for the attr
leaf and da node blocks.  Can you please fish out the second magic and
print that too?

Looks otherwise reasonable, and certainly better than the ASSERT.

--D

> +	{ NULL }
> +};
> +
>  /* Set the CRC. */
>  void
>  xfs_attr3_set_crc(
> diff --git a/db/attr.h b/db/attr.h
> index ba23480c..a8566a8c 100644
> --- a/db/attr.h
> +++ b/db/attr.h
> @@ -33,6 +33,7 @@ extern const field_t	attr3_node_hdr_flds[];
>  extern const field_t	attr3_blkinfo_flds[];
>  extern const field_t	attr3_node_hdr_flds[];
>  extern const field_t	attr3_remote_crc_flds[];
> +extern const field_t	attr3_unkown_flds[];
>  
>  extern int	attr_leaf_name_size(void *obj, int startoff, int idx);
>  extern int	attr_size(void *obj, int startoff, int idx);
> diff --git a/db/field.c b/db/field.c
> index ae4c8057..388bcbe1 100644
> --- a/db/field.c
> +++ b/db/field.c
> @@ -102,6 +102,8 @@ const ftattr_t	ftattrtab[] = {
>  	{ FLDT_ATTR3_REMOTE_HDR, "attr3_remote_hdr", NULL,
>  	  (char *)attr3_remote_crc_flds, attr_size, FTARG_SIZE, NULL,
>  	  attr3_remote_crc_flds },
> +	{ FLDT_ATTR3_UNKOWN_HDR, "attr3_unkown_hdr", NULL,
> +	  NULL, NULL, FTARG_SIZE, NULL, attr3_unkown_flds},
>  
>  	{ FLDT_BMAPBTA, "bmapbta", NULL, (char *)bmapbta_flds, btblock_size,
>  	  FTARG_SIZE, NULL, bmapbta_flds },
> diff --git a/db/field.h b/db/field.h
> index a8df29bc..291ef2e5 100644
> --- a/db/field.h
> +++ b/db/field.h
> @@ -48,6 +48,7 @@ typedef enum fldt	{
>  	FLDT_ATTR3_LEAF_HDR,
>  	FLDT_ATTR3_NODE_HDR,
>  	FLDT_ATTR3_REMOTE_HDR,
> +	FLDT_ATTR3_UNKOWN_HDR,
>  
>  	FLDT_BMAPBTA,
>  	FLDT_BMAPBTA_CRC,
> -- 
> 2.14.3
> 
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