From: Darrick J. Wong <darrick.wong@oracle.com>
Date: Mon, 31 Jul 2017 20:08:12 +0000 (-0500)
Subject: xfs: don't crash on unexpected holes in dir/attr btrees
X-Git-Tag: v4.13.0-rc1~47
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=a6c6b1bd72f63b2bb05cae185abef0da24e0bf28;p=users%2Fhch%2Fxfsprogs.git

xfs: don't crash on unexpected holes in dir/attr btrees

Source kernel commit: cd87d867920155911d0d2e6485b769d853547750

In quite a few places we call xfs_da_read_buf with a mappedbno that we
don't control, then assume that the function passes back either an error
code or a buffer pointer.  Unfortunately, if mappedbno == -2 and bno
maps to a hole, we get a return code of zero and a NULL buffer, which
means that we crash if we actually try to use that buffer pointer.  This
happens immediately when we set the buffer type for transaction context.

Therefore, check that we have no error code and a non-NULL bp before
trying to use bp.  This patch is a follow-up to an incomplete fix in
96a3aefb8ffde231 ("xfs: don't crash if reading a directory results in an
unexpected hole").

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
---

diff --git a/libxfs/xfs_attr_leaf.c b/libxfs/xfs_attr_leaf.c
index 246d5b45b..6053b56a9 100644
--- a/libxfs/xfs_attr_leaf.c
+++ b/libxfs/xfs_attr_leaf.c
@@ -346,7 +346,7 @@ xfs_attr3_leaf_read(
 
 	err = xfs_da_read_buf(tp, dp, bno, mappedbno, bpp,
 				XFS_ATTR_FORK, &xfs_attr3_leaf_buf_ops);
-	if (!err && tp)
+	if (!err && tp && *bpp)
 		xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_ATTR_LEAF_BUF);
 	return err;
 }
diff --git a/libxfs/xfs_da_btree.c b/libxfs/xfs_da_btree.c
index a54304550..347bf4821 100644
--- a/libxfs/xfs_da_btree.c
+++ b/libxfs/xfs_da_btree.c
@@ -258,7 +258,7 @@ xfs_da3_node_read(
 
 	err = xfs_da_read_buf(tp, dp, bno, mappedbno, bpp,
 					which_fork, &xfs_da3_node_buf_ops);
-	if (!err && tp) {
+	if (!err && tp && *bpp) {
 		struct xfs_da_blkinfo	*info = (*bpp)->b_addr;
 		int			type;
 
diff --git a/libxfs/xfs_dir2_block.c b/libxfs/xfs_dir2_block.c
index 32bde3115..2da5f1a3f 100644
--- a/libxfs/xfs_dir2_block.c
+++ b/libxfs/xfs_dir2_block.c
@@ -135,7 +135,7 @@ xfs_dir3_block_read(
 
 	err = xfs_da_read_buf(tp, dp, mp->m_dir_geo->datablk, -1, bpp,
 				XFS_DATA_FORK, &xfs_dir3_block_buf_ops);
-	if (!err && tp)
+	if (!err && tp && *bpp)
 		xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_DIR_BLOCK_BUF);
 	return err;
 }
diff --git a/libxfs/xfs_dir2_leaf.c b/libxfs/xfs_dir2_leaf.c
index e93f12a22..5e9cf9010 100644
--- a/libxfs/xfs_dir2_leaf.c
+++ b/libxfs/xfs_dir2_leaf.c
@@ -265,7 +265,7 @@ xfs_dir3_leaf_read(
 
 	err = xfs_da_read_buf(tp, dp, fbno, mappedbno, bpp,
 				XFS_DATA_FORK, &xfs_dir3_leaf1_buf_ops);
-	if (!err && tp)
+	if (!err && tp && *bpp)
 		xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_DIR_LEAF1_BUF);
 	return err;
 }
@@ -282,7 +282,7 @@ xfs_dir3_leafn_read(
 
 	err = xfs_da_read_buf(tp, dp, fbno, mappedbno, bpp,
 				XFS_DATA_FORK, &xfs_dir3_leafn_buf_ops);
-	if (!err && tp)
+	if (!err && tp && *bpp)
 		xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_DIR_LEAFN_BUF);
 	return err;
 }