[PATCH 3/3] fs: ocfs2: Fix a possible null-pointer dereference in ocfs2_info_scan_inode_alloc()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

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.       

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 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 d6f7b299eb23..efeea208fdeb 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -283,7 +283,7 @@ static int ocfs2_info_scan_inode_alloc(struct ocfs2_super *osb,
 	if (inode_alloc)
 		inode_lock(inode_alloc);
 
-	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);
-- 
2.17.0