[PATCH AUTOSEL 4.4 15/21] fs: ocfs2: fix a possible null-pointer dereference in ocfs2_info_scan_inode_alloc()

[Sasha Levin]

From: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>

[ 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@xxxxxxxxx
Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Mark Fasheh <mark@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Changwei Ge <gechangwei@xxxxxxx>
Cc: Gang He <ghe@xxxxxxxx>
Cc: Jun Piao <piaojun@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/ocfs2/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index 3cb097ccce607..79232296b7d2b 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -289,7 +289,7 @@ static int ocfs2_info_scan_inode_alloc(struct ocfs2_super *osb,
 	if (inode_alloc)
 		mutex_lock(&inode_alloc->i_mutex);
 
-	if (o2info_coherent(&fi->ifi_req)) {
+	if (inode_alloc && o2info_coherent(&fi->ifi_req)) {
 		status = ocfs2_inode_lock(inode_alloc, &bh, 0);
 		if (status < 0) {
 			mlog_errno(status);
-- 
2.20.1