[PATCH v3] hfs: handle extent B-tree write errors

[Davy Felipe <davyfelipe34@gmail.com>]

hfs_brec_insert() may fail while inserting a new extent record, but
__hfs_ext_write_extent() currently ignores its return value and clears
HFS_FLG_EXT_DIRTY and HFS_FLG_EXT_NEW as if the insertion had
succeeded.

Propagate errors returned by hfs_brec_insert() and only clear the
extent flags after a successful insertion.

When updating an existing extent record, hfs_bnode_write() returns
void. The helper may reject an invalid offset or shorten an overlong
write without returning status to its caller. Validate the extent
record length and write range before calling hfs_bnode_write() so an
invalid update is reported as -EIO instead of being treated as
successful.

Negative-path testing in QEMU confirmed that an insertion error is
propagated to the caller. Testing the existing-record path also
confirmed that invalid write parameters are rejected before
HFS_FLG_EXT_DIRTY is cleared.

Signed-off-by: Davy Felipe <davyfelipe34@gmail.com>

Changes in v3:
- Preserve the original insertion-error propagation.
- Validate the existing extent record before hfs_bnode_write().
- Return -EIO for invalid extent write parameters instead of clearing
  HFS_FLG_EXT_DIRTY after a rejected write.
- Clarify that hfs_bnode_write() returns void and therefore has no
  error value for this caller to propagate.
- Keep test-only instrumentation outside the submitted patch.

---
 fs/hfs/extent.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/hfs/extent.c b/fs/hfs/extent.c
index f066a99a863b..13426503fbb3 100644
--- a/fs/hfs/extent.c
+++ b/fs/hfs/extent.c
@@ -121,12 +121,21 @@ static int __hfs_ext_write_extent(struct inode *inode, struct hfs_find_data *fd)
 		res = hfs_bmap_reserve(fd->tree, fd->tree->depth + 1);
 		if (res)
 			return res;
-		hfs_brec_insert(fd, HFS_I(inode)->cached_extents, sizeof(hfs_extent_rec));
+		res = hfs_brec_insert(fd, HFS_I(inode)->cached_extents,
+				      sizeof(hfs_extent_rec));
+		if (res)
+			return res;
 		HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
 	} else {
 		if (res)
 			return res;
-		hfs_bnode_write(fd->bnode, HFS_I(inode)->cached_extents, fd->entryoffset, fd->entrylength);
+		if (fd->entrylength != sizeof(hfs_extent_rec) ||
+		    fd->entryoffset < 0 ||
+		    (u64)fd->entryoffset + fd->entrylength >
+			    fd->tree->node_size)
+			return -EIO;
+		hfs_bnode_write(fd->bnode, HFS_I(inode)->cached_extents,
+				fd->entryoffset, fd->entrylength);
 		HFS_I(inode)->flags &= ~HFS_FLG_EXT_DIRTY;
 	}
 	return 0;
-- 
2.55.0