Re: [PATCH v3 1/3] xfs: ensure logflagsp is initialized in xfs_bmap_del_extent_real

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Nov 30, 2023 at 12:05:14PM +0800, Jiachen Zhang wrote:
> In the case of returning -ENOSPC, ensure logflagsp is initialized by 0.
> Otherwise the caller __xfs_bunmapi will set uninitialized illegal
> tmp_logflags value into xfs log, which might cause unpredictable error
> in the log recovery procedure.
> 
> Also, remove the flags variable and set the *logflagsp directly, so that
> the code should be more robust in the long run.
> 
> Fixes: 1b24b633aafe ("xfs: move some more code into xfs_bmap_del_extent_real")
> Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks good,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/libxfs/xfs_bmap.c | 73 +++++++++++++++++-----------------------
>  1 file changed, 31 insertions(+), 42 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index be62acffad6c..eacd7f43c952 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -5010,7 +5010,6 @@ xfs_bmap_del_extent_real(
>  	xfs_fileoff_t		del_endoff;	/* first offset past del */
>  	int			do_fx;	/* free extent at end of routine */
>  	int			error;	/* error return value */
> -	int			flags = 0;/* inode logging flags */
>  	struct xfs_bmbt_irec	got;	/* current extent entry */
>  	xfs_fileoff_t		got_endoff;	/* first offset past got */
>  	int			i;	/* temp state */
> @@ -5023,6 +5022,8 @@ xfs_bmap_del_extent_real(
>  	uint32_t		state = xfs_bmap_fork_to_state(whichfork);
>  	struct xfs_bmbt_irec	old;
>  
> +	*logflagsp = 0;
> +
>  	mp = ip->i_mount;
>  	XFS_STATS_INC(mp, xs_del_exlist);
>  
> @@ -5035,7 +5036,6 @@ xfs_bmap_del_extent_real(
>  	ASSERT(got_endoff >= del_endoff);
>  	ASSERT(!isnullstartblock(got.br_startblock));
>  	qfield = 0;
> -	error = 0;
>  
>  	/*
>  	 * If it's the case where the directory code is running with no block
> @@ -5051,13 +5051,13 @@ xfs_bmap_del_extent_real(
>  	    del->br_startoff > got.br_startoff && del_endoff < got_endoff)
>  		return -ENOSPC;
>  
> -	flags = XFS_ILOG_CORE;
> +	*logflagsp = XFS_ILOG_CORE;
>  	if (whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip)) {
>  		if (!(bflags & XFS_BMAPI_REMAP)) {
>  			error = xfs_rtfree_blocks(tp, del->br_startblock,
>  					del->br_blockcount);
>  			if (error)
> -				goto done;
> +				return error;
>  		}
>  
>  		do_fx = 0;
> @@ -5072,11 +5072,9 @@ xfs_bmap_del_extent_real(
>  	if (cur) {
>  		error = xfs_bmbt_lookup_eq(cur, &got, &i);
>  		if (error)
> -			goto done;
> -		if (XFS_IS_CORRUPT(mp, i != 1)) {
> -			error = -EFSCORRUPTED;
> -			goto done;
> -		}
> +			return error;
> +		if (XFS_IS_CORRUPT(mp, i != 1))
> +			return -EFSCORRUPTED;
>  	}
>  
>  	if (got.br_startoff == del->br_startoff)
> @@ -5093,17 +5091,15 @@ xfs_bmap_del_extent_real(
>  		xfs_iext_prev(ifp, icur);
>  		ifp->if_nextents--;
>  
> -		flags |= XFS_ILOG_CORE;
> +		*logflagsp |= XFS_ILOG_CORE;
>  		if (!cur) {
> -			flags |= xfs_ilog_fext(whichfork);
> +			*logflagsp |= xfs_ilog_fext(whichfork);
>  			break;
>  		}
>  		if ((error = xfs_btree_delete(cur, &i)))
> -			goto done;
> -		if (XFS_IS_CORRUPT(mp, i != 1)) {
> -			error = -EFSCORRUPTED;
> -			goto done;
> -		}
> +			return error;
> +		if (XFS_IS_CORRUPT(mp, i != 1))
> +			return -EFSCORRUPTED;
>  		break;
>  	case BMAP_LEFT_FILLING:
>  		/*
> @@ -5114,12 +5110,12 @@ xfs_bmap_del_extent_real(
>  		got.br_blockcount -= del->br_blockcount;
>  		xfs_iext_update_extent(ip, state, icur, &got);
>  		if (!cur) {
> -			flags |= xfs_ilog_fext(whichfork);
> +			*logflagsp |= xfs_ilog_fext(whichfork);
>  			break;
>  		}
>  		error = xfs_bmbt_update(cur, &got);
>  		if (error)
> -			goto done;
> +			return error;
>  		break;
>  	case BMAP_RIGHT_FILLING:
>  		/*
> @@ -5128,12 +5124,12 @@ xfs_bmap_del_extent_real(
>  		got.br_blockcount -= del->br_blockcount;
>  		xfs_iext_update_extent(ip, state, icur, &got);
>  		if (!cur) {
> -			flags |= xfs_ilog_fext(whichfork);
> +			*logflagsp |= xfs_ilog_fext(whichfork);
>  			break;
>  		}
>  		error = xfs_bmbt_update(cur, &got);
>  		if (error)
> -			goto done;
> +			return error;
>  		break;
>  	case 0:
>  		/*
> @@ -5150,18 +5146,18 @@ xfs_bmap_del_extent_real(
>  		new.br_state = got.br_state;
>  		new.br_startblock = del_endblock;
>  
> -		flags |= XFS_ILOG_CORE;
> +		*logflagsp |= XFS_ILOG_CORE;
>  		if (cur) {
>  			error = xfs_bmbt_update(cur, &got);
>  			if (error)
> -				goto done;
> +				return error;
>  			error = xfs_btree_increment(cur, 0, &i);
>  			if (error)
> -				goto done;
> +				return error;
>  			cur->bc_rec.b = new;
>  			error = xfs_btree_insert(cur, &i);
>  			if (error && error != -ENOSPC)
> -				goto done;
> +				return error;
>  			/*
>  			 * If get no-space back from btree insert, it tried a
>  			 * split, and we have a zero block reservation.  Fix up
> @@ -5174,33 +5170,28 @@ xfs_bmap_del_extent_real(
>  				 */
>  				error = xfs_bmbt_lookup_eq(cur, &got, &i);
>  				if (error)
> -					goto done;
> -				if (XFS_IS_CORRUPT(mp, i != 1)) {
> -					error = -EFSCORRUPTED;
> -					goto done;
> -				}
> +					return error;
> +				if (XFS_IS_CORRUPT(mp, i != 1))
> +					return -EFSCORRUPTED;
>  				/*
>  				 * Update the btree record back
>  				 * to the original value.
>  				 */
>  				error = xfs_bmbt_update(cur, &old);
>  				if (error)
> -					goto done;
> +					return error;
>  				/*
>  				 * Reset the extent record back
>  				 * to the original value.
>  				 */
>  				xfs_iext_update_extent(ip, state, icur, &old);
> -				flags = 0;
> -				error = -ENOSPC;
> -				goto done;
> -			}
> -			if (XFS_IS_CORRUPT(mp, i != 1)) {
> -				error = -EFSCORRUPTED;
> -				goto done;
> +				*logflagsp = 0;
> +				return -ENOSPC;
>  			}
> +			if (XFS_IS_CORRUPT(mp, i != 1))
> +				return -EFSCORRUPTED;
>  		} else
> -			flags |= xfs_ilog_fext(whichfork);
> +			*logflagsp |= xfs_ilog_fext(whichfork);
>  
>  		ifp->if_nextents++;
>  		xfs_iext_next(ifp, icur);
> @@ -5224,7 +5215,7 @@ xfs_bmap_del_extent_real(
>  					((bflags & XFS_BMAPI_NODISCARD) ||
>  					del->br_state == XFS_EXT_UNWRITTEN));
>  			if (error)
> -				goto done;
> +				return error;
>  		}
>  	}
>  
> @@ -5239,9 +5230,7 @@ xfs_bmap_del_extent_real(
>  	if (qfield && !(bflags & XFS_BMAPI_REMAP))
>  		xfs_trans_mod_dquot_byino(tp, ip, qfield, (long)-nblks);
>  
> -done:
> -	*logflagsp = flags;
> -	return error;
> +	return 0;
>  }
>  
>  /*
> -- 
> 2.20.1
> 
>