FS: JFS: Check for read-only mounted filesystem in txBegin

[ 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@gmail.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
index 224ef034004b7d28a5fcdcc9d1aefe100b92ff7a..2cb460912468e19a6794e063ddce63814a387975 100644 (file)
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -367,6 +367,11 @@ 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);