linux-kernel - [PATCH] jfs: fix uninitialized waitqueue in transaction manager

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Message-ID: <20250824201332.4236-1-ssrane_b23@ee.vjti.ac.in>
Date: Mon, 25 Aug 2025 01:43:32 +0530
From: Shaurya Rane <ssrane_b23@...vjti.ac.in>
To: shaggy@...nel.org
Cc: jfs-discussion@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	syzbot+0cee785b798102696a4b@...kaller.appspotmail.com,
	Shaurya Rane <ssrane_b23@...vjti.ac.in>,
	syzbot+c4f3462d8b2ad7977bea@...kaller.appspotmail.com
Subject: [PATCH] jfs: fix uninitialized waitqueue in transaction manager

The transaction manager initialization in txInit() was not properly
initializing TxBlock[0].waitor waitqueue, causing a crash when
txEnd(0) is called on read-only filesystems.

When a filesystem is mounted read-only, txBegin() returns tid=0 to
indicate no transaction. However, txEnd(0) still gets called and
tries to access TxBlock[0].waitor via tid_to_tblock(0), but this
waitqueue was never initialized because the initialization loop
started at index 1 instead of 0.

This causes a 'non-static key' lockdep warning and system crash:
  INFO: trying to register non-static key in txEnd

Fix by ensuring all transaction blocks including TxBlock[0] have
their waitqueues properly initialized during txInit().

Reported-by: syzbot+c4f3462d8b2ad7977bea@...kaller.appspotmail.com

Signed-off-by: Shaurya Rane <ssrane_b23@...vjti.ac.in>
---
 fs/jfs/jfs_txnmgr.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
index be17e3c43582..7840a03e5bcb 100644
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -272,14 +272,15 @@ int txInit(void)
 	if (TxBlock == NULL)
 		return -ENOMEM;
 
-	for (k = 1; k < nTxBlock - 1; k++) {
-		TxBlock[k].next = k + 1;
+	for (k = 0; k < nTxBlock; k++) {
 		init_waitqueue_head(&TxBlock[k].gcwait);
 		init_waitqueue_head(&TxBlock[k].waitor);
 	}
+
+	for (k = 1; k < nTxBlock - 1; k++) {
+		TxBlock[k].next = k + 1;
+	}
 	TxBlock[k].next = 0;
-	init_waitqueue_head(&TxBlock[k].gcwait);
-	init_waitqueue_head(&TxBlock[k].waitor);
 
 	TxAnchor.freetid = 1;
 	init_waitqueue_head(&TxAnchor.freewait);
-- 
2.34.1