fs: ocfs2: fix a possible null-pointer dereference in ocfs2_info_scan_inode_alloc()

fs: ocfs2: fix a possible null-pointer dereference in ocfs2_info_scan_inode_alloc()

[ Upstream commit 2abb7d3b12d007c30193f48bebed781009bebdd2 ]

In ocfs2_info_scan_inode_alloc(), there is an if statement on line 283
to check whether inode_alloc is NULL:

    if (inode_alloc)

When inode_alloc is NULL, it is used on line 287:

    ocfs2_inode_lock(inode_alloc, &bh, 0);
        ocfs2_inode_lock_full_nested(inode, ...)
            struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

Thus, a possible null-pointer dereference may occur.

To fix this bug, inode_alloc is checked on line 286.

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

Link: http://lkml.kernel.org/r/20190726033717.32359-1-baijiaju1990@gmail.com
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>