Re: [PATCH 2/5] xfs_repair: fix unaligned accesses

[Brian Foster <bfoster@redhat.com>]

On Fri, Oct 09, 2015 at 02:51:09PM -0500, Eric Sandeen wrote:
> This fixes some unaligned accesses spotted by libubsan in repair.
> 
> See Documentation/unaligned-memory-access.txt in the kernel
> tree for why these can be a problem.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> 
> V2: 
> Add note about why ...
> Add another in libxfs_bmbt_disk_get_all
> Fix mistaken double-swap in dinode.c in original patch
> 
>  include/libxfs.h  |  4 ++--
>  repair/dinode.c   | 47 ++++++++++++++++++++++++-----------------------
>  repair/prefetch.c |  4 ++--
>  3 files changed, 28 insertions(+), 27 deletions(-)
> 
> diff --git a/include/libxfs.h b/include/libxfs.h
> index b1604e2..52fb483 100644
> --- a/include/libxfs.h
> +++ b/include/libxfs.h
> @@ -206,8 +206,8 @@ libxfs_bmbt_disk_get_all(
>  {
>  	struct xfs_bmbt_rec_host hrec;
>  
> -	hrec.l0 = be64_to_cpu(rp->l0);
> -	hrec.l1 = be64_to_cpu(rp->l1);
> +	hrec.l0 = get_unaligned_be64(&rp->l0);
> +	hrec.l1 = get_unaligned_be64(&rp->l1);
>  	libxfs_bmbt_get_all(&hrec, irec);
>  }
>  
> diff --git a/repair/dinode.c b/repair/dinode.c
> index f78f907..f99cba3 100644
> --- a/repair/dinode.c
> +++ b/repair/dinode.c
> @@ -960,15 +960,17 @@ _("bad numrecs 0 in inode %" PRIu64 " bmap btree root block\n"),
>  		 * btree, we'd do it right here.  For now, if there's a
>  		 * problem, we'll bail out and presumably clear the inode.
>  		 */
> -		if (!verify_dfsbno(mp, be64_to_cpu(pp[i])))  {
> -			do_warn(_("bad bmap btree ptr 0x%llx in ino %" PRIu64 "\n"),
> -			       (unsigned long long) be64_to_cpu(pp[i]), lino);
> +		if (!verify_dfsbno(mp, get_unaligned_be64(&pp[i])))  {
> +			do_warn(
> +("bad bmap btree ptr 0x%" PRIx64 " in ino %" PRIu64 "\n"),
> +				get_unaligned_be64(&pp[i]), lino);
>  			return(1);
>  		}
>  
> -		if (scan_lbtree(be64_to_cpu(pp[i]), level, scan_bmapbt, type,
> -				whichfork, lino, tot, nex, blkmapp, &cursor,
> -				1, check_dups, magic, &xfs_bmbt_buf_ops))
> +		if (scan_lbtree(get_unaligned_be64(&pp[i]), level, scan_bmapbt,
> +				type, whichfork, lino, tot, nex, blkmapp,
> +				&cursor, 1, check_dups, magic,
> +				&xfs_bmbt_buf_ops))
>  			return(1);
>  		/*
>  		 * fix key (offset) mismatches between the keys in root
> @@ -977,28 +979,27 @@ _("bad numrecs 0 in inode %" PRIu64 " bmap btree root block\n"),
>  		 * blocks but the parent hasn't been updated
>  		 */
>  		if (!check_dups && cursor.level[level-1].first_key !=
> -					be64_to_cpu(pkey[i].br_startoff))  {
> +				   get_unaligned_be64(&pkey[i].br_startoff)) {
>  			if (!no_modify)  {
>  				do_warn(
> -	_("correcting key in bmbt root (was %llu, now %" PRIu64") in inode "
> -	  "%" PRIu64" %s fork\n"),
> -				       (unsigned long long)
> -					       be64_to_cpu(pkey[i].br_startoff),
> -					cursor.level[level-1].first_key,
> -					XFS_AGINO_TO_INO(mp, agno, ino),
> -					forkname);
> +_("correcting key in bmbt root (was %" PRIu64 ", now %" PRIu64") in inode "
> +  "%" PRIu64" %s fork\n"),
> +				       get_unaligned_be64(&pkey[i].br_startoff),
> +				       cursor.level[level-1].first_key,
> +				       XFS_AGINO_TO_INO(mp, agno, ino),
> +				       forkname);
>  				*dirty = 1;
> -				pkey[i].br_startoff = cpu_to_be64(
> -					cursor.level[level-1].first_key);
> +				put_unaligned_be64(
> +					cursor.level[level-1].first_key,
> +					&pkey[i].br_startoff);
>  			} else  {
>  				do_warn(
> -	_("bad key in bmbt root (is %llu, would reset to %" PRIu64 ") in inode "
> -	  "%" PRIu64 " %s fork\n"),
> -				       (unsigned long long)
> -					       be64_to_cpu(pkey[i].br_startoff),
> -					cursor.level[level-1].first_key,
> -					XFS_AGINO_TO_INO(mp, agno, ino),
> -					forkname);
> +_("bad key in bmbt root (is %" PRIu64 ", would reset to %" PRIu64 ") in inode "
> +  "%" PRIu64 " %s fork\n"),
> +				       get_unaligned_be64(&pkey[i].br_startoff),
> +				       cursor.level[level-1].first_key,
> +				       XFS_AGINO_TO_INO(mp, agno, ino),
> +				       forkname);
>  			}
>  		}
>  		/*
> diff --git a/repair/prefetch.c b/repair/prefetch.c
> index 32ec55e..52238ca 100644
> --- a/repair/prefetch.c
> +++ b/repair/prefetch.c
> @@ -330,7 +330,7 @@ pf_scanfunc_bmap(
>  	pp = XFS_BMBT_PTR_ADDR(mp, block, 1, mp->m_bmap_dmxr[1]);
>  
>  	for (i = 0; i < numrecs; i++) {
> -		dbno = be64_to_cpu(pp[i]);
> +		dbno = get_unaligned_be64(&pp[i]);
>  		if (!verify_dfsbno(mp, dbno))
>  			return 0;
>  		if (!pf_scan_lbtree(dbno, level, isadir, args, pf_scanfunc_bmap))
> @@ -372,7 +372,7 @@ pf_read_btinode(
>  	pp = XFS_BMDR_PTR_ADDR(dib, 1, xfs_bmdr_maxrecs(dsize, 0));
>  
>  	for (i = 0; i < numrecs; i++) {
> -		dbno = be64_to_cpu(pp[i]);
> +		dbno = get_unaligned_be64(&pp[i]);
>  		if (!verify_dfsbno(mp, dbno))
>  			break;
>  		if (!pf_scan_lbtree(dbno, level, isadir, args, pf_scanfunc_bmap))
> -- 
> 2.6.1
> 
> 
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