[PATCH AUTOSEL 5.6 027/129] xfs: fix regression in "cleanup xfs_dir2_block_getdents"

Sasha Levin
2020-04-15T13:16:06Z

From: Tommi Rantala <tommi.t.rantala@nokia.com>

[ Upstream commit 3d28e7e278913a267b1de360efcd5e5274065ce2 ]

Commit 263dde869bd09 ("xfs: cleanup xfs_dir2_block_getdents") introduced
a getdents regression, when it converted the pointer arithmetics to
offset calculations: offset is updated in the loop already for the next
iteration, but the updated offset value is used incorrectly in two
places, where we should have used the not-yet-updated value.

This caused for example "git clean -ffdx" failures to cleanup certain
directory structures when running in a container.

Fix the regression by making sure we use proper offset in the loop body.
Thanks to Christoph Hellwig for suggestion how to best fix the code.

Cc: Christoph Hellwig <hch@lst.de>
Fixes: 263dde869bd09 ("xfs: cleanup xfs_dir2_block_getdents")
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/xfs/xfs_dir2_readdir.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
index 0d3b640cf1cce..871ec22c9aee9 100644
--- a/fs/xfs/xfs_dir2_readdir.c
+++ b/fs/xfs/xfs_dir2_readdir.c
@@ -147,7 +147,7 @@ xfs_dir2_block_getdents(
xfs_off_t cook;
struct xfs_da_geometry *geo = args->geo;
int lock_mode;
- unsigned int offset;
+ unsigned int offset, next_offset;
unsigned int end;

/*
@@ -173,9 +173,10 @@ xfs_dir2_block_getdents(
* Loop over the data portion of the block.
* Each object is a real entry (dep) or an unused one (dup).
*/
- offset = geo->data_entry_offset;
end = xfs_dir3_data_end_offset(geo, bp->b_addr);
- while (offset < end) {
+ for (offset = geo->data_entry_offset;
+ offset < end;
+ offset = next_offset) {
struct xfs_dir2_data_unused *dup = bp->b_addr + offset;
struct xfs_dir2_data_entry *dep = bp->b_addr + offset;
uint8_t filetype;
@@ -184,14 +185,15 @@ xfs_dir2_block_getdents(
* Unused, skip it.
*/
if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
- offset += be16_to_cpu(dup->length);
+ next_offset = offset + be16_to_cpu(dup->length);
continue;
}

/*
* Bump pointer for the next iteration.
*/
- offset += xfs_dir2_data_entsize(dp->i_mount, dep->namelen);
+ next_offset = offset +
+ xfs_dir2_data_entsize(dp->i_mount, dep->namelen);

/*
* The entry is before the desired starting point, skip it.
--
2.20.1