linux-kernel - [PATCH 2/3] fs: ocfs2: Fix a possible null-pointer dereference in ocfs2_write_end

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Date:   Fri, 26 Jul 2019 11:37:05 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     mark@...heh.com, jlbec@...lplan.org, joseph.qi@...ux.alibaba.com
Cc:     ocfs2-devel@....oracle.com, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/3] fs: ocfs2: Fix a possible null-pointer dereference in ocfs2_write_end_nolock()

In ocfs2_write_end_nolock(), there are an if statement on lines 1976, 
2047 and 2058, to check whether handle is NULL:
    if (handle)

When handle is NULL, it is used on line 2045:
	ocfs2_update_inode_fsync_trans(handle, inode, 1);
        oi->i_sync_tid = handle->h_transaction->t_tid;

Thus, a possible null-pointer dereference may occur.

To fix this bug, handle is checked before calling
ocfs2_update_inode_fsync_trans().

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 fs/ocfs2/aops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index a4c905d6b575..5473bd99043e 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -2042,7 +2042,8 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
 		inode->i_mtime = inode->i_ctime = current_time(inode);
 		di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
 		di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
-		ocfs2_update_inode_fsync_trans(handle, inode, 1);
+		if (handle)
+			ocfs2_update_inode_fsync_trans(handle, inode, 1);
 	}
 	if (handle)
 		ocfs2_journal_dirty(handle, wc->w_di_bh);
-- 
2.17.0