linux-kernel - [PATCH AUTOSEL 5.15 23/23] FS: JFS: Check for read-only mounted filesystem in txBegin

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Message-Id: <20230724012334.2317140-23-sashal@kernel.org>
Date:   Sun, 23 Jul 2023 21:23:34 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Immad Mir <mirimmad17@...il.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Sasha Levin <sashal@...nel.org>, shaggy@...nel.org,
        jfs-discussion@...ts.sourceforge.net
Subject: [PATCH AUTOSEL 5.15 23/23] FS: JFS: Check for read-only mounted filesystem in txBegin

From: Immad Mir <mirimmad17@...il.com>

[ Upstream commit 95e2b352c03b0a86c5717ba1d24ea20969abcacc ]

 This patch adds a check for read-only mounted filesystem
 in txBegin before starting a transaction potentially saving
 from NULL pointer deref.

Signed-off-by: Immad Mir <mirimmad17@...il.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/jfs/jfs_txnmgr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
index 042bbe6d8ac2e..6c8680d3907af 100644
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -354,6 +354,11 @@ tid_t txBegin(struct super_block *sb, int flag)
 	jfs_info("txBegin: flag = 0x%x", flag);
 	log = JFS_SBI(sb)->log;
 
+	if (!log) {
+		jfs_error(sb, "read-only filesystem\n");
+		return 0;
+	}
+
 	TXN_LOCK();
 
 	INCREMENT(TxStat.txBegin);
-- 
2.39.2