[PATCH 2/2] Cygwin: flock: Fix overlap handling in lf_setlock() and lf_clearlock()

[Takashi Yano]

Currently, create_lock_obj() can create multiple locks with the same
lock range that have different version number. However, lf_setlock()
and lf_clearlock() cannot handle this case appropriately. With this
patch, make lf_setlock() and lf_clearlock() find overlap again even
when ovcase = 1 (lock and overlap have the same lock range).

Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256750.html
Fixes: 2e560a092c1c ("* flock.cc (LOCK_OBJ_NAME_LEN): Change to accommodate extra lf_ver field.")
Reported-by: Sebastian Feld <sebastian.n.feld@gmail.com>
Reviewed-by:
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/flock.cc | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/winsup/cygwin/flock.cc b/winsup/cygwin/flock.cc
index 794e66bd7..5f703ad0e 100644
--- a/winsup/cygwin/flock.cc
+++ b/winsup/cygwin/flock.cc
@@ -1411,11 +1411,10 @@ lf_setlock (lockf_t *lock, inode_t *node, lockf_t **clean, HANDLE fhdl)
 	  if (lock_cnt > MAX_LOCKF_CNT - room_for_clearlock)
 	    return ENOLCK;
 	  lf_wakelock (overlap, fhdl);
-	  overlap->lf_type = lock->lf_type;
-	  overlap->create_lock_obj ();
-	  lock->lf_next = *clean;
-	  *clean = lock;
-	  break;
+	  *prev = overlap->lf_next;
+	  overlap->lf_next = *clean;
+	  *clean = overlap;
+	  continue;
 
 	case 2: /* overlap contains lock */
 	  /*
@@ -1564,9 +1563,11 @@ lf_clearlock (lockf_t *unlock, lockf_t **clean, HANDLE fhdl)
 	{
 	case 1: /* overlap == lock */
 	  *prev = overlap->lf_next;
+	  lf = overlap->lf_next;
 	  overlap->lf_next = *clean;
 	  *clean = overlap;
-	  break;
+	  first_loop = false;
+	  continue;
 
 	case 2: /* overlap contains lock: split it */
 	  if (overlap->lf_start == unlock->lf_start)
-- 
2.45.1