[PATCH AUTOSEL 4.19 2/5] gfs2: Fix invalid metadata access in punch_hole

[Sasha Levin]

From: Andrew Price <anprice@xxxxxxxxxx>

[ Upstream commit c95346ac918c5badf51b9a7ac58a26d3bd5bb224 ]

In punch_hole(), when the offset lies in the final block for a given
height, there is no hole to punch, but the maximum size check fails to
detect that.  Consequently, punch_hole() will try to punch a hole beyond
the end of the metadata and fail.  Fix the maximum size check.

Signed-off-by: Andrew Price <anprice@xxxxxxxxxx>
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/gfs2/bmap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 729f36fdced1f..b365828328df0 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -1751,7 +1751,8 @@ static int punch_hole(struct gfs2_inode *ip, u64 offset, u64 length)
 	struct buffer_head *dibh, *bh;
 	struct gfs2_holder rd_gh;
 	unsigned int bsize_shift = sdp->sd_sb.sb_bsize_shift;
-	u64 lblock = (offset + (1 << bsize_shift) - 1) >> bsize_shift;
+	unsigned int bsize = 1 << bsize_shift;
+	u64 lblock = (offset + bsize - 1) >> bsize_shift;
 	__u16 start_list[GFS2_MAX_META_HEIGHT];
 	__u16 __end_list[GFS2_MAX_META_HEIGHT], *end_list = NULL;
 	unsigned int start_aligned, end_aligned;
@@ -1762,7 +1763,7 @@ static int punch_hole(struct gfs2_inode *ip, u64 offset, u64 length)
 	u64 prev_bnr = 0;
 	__be64 *start, *end;
 
-	if (offset >= maxsize) {
+	if (offset + bsize - 1 >= maxsize) {
 		/*
 		 * The starting point lies beyond the allocated meta-data;
 		 * there are no blocks do deallocate.
-- 
2.43.0