[PATCH] hugetlb: fix NULL pointer dereference in trace_hugetlbfs_alloc_inode

[Muchun Song]

hugetlb_file_setup() will pass a NULL @dir to hugetlbfs_get_inode(), so
we will access a NULL pointer for @dir. Fix it and set __entry->dr to
0 if @dir is NULL. Because ->i_ino cannot be 0 (see get_next_ino()),
there is no confusing if user sees a 0 inode number.

Fixes: 318580ad7f28 ("hugetlbfs: support tracepoint")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Cheung Wall <zzqq0103.hey@xxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/02858D60-43C1-4863-A84F-3C76A8AF1F15@xxxxxxxxx/T/#
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 include/trace/events/hugetlbfs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/hugetlbfs.h b/include/trace/events/hugetlbfs.h
index 8331c904a9ba8..59605dfaeeb43 100644
--- a/include/trace/events/hugetlbfs.h
+++ b/include/trace/events/hugetlbfs.h
@@ -23,7 +23,7 @@ TRACE_EVENT(hugetlbfs_alloc_inode,
 	TP_fast_assign(
 		__entry->dev		= inode->i_sb->s_dev;
 		__entry->ino		= inode->i_ino;
-		__entry->dir		= dir->i_ino;
+		__entry->dir		= dir ? dir->i_ino : 0;
 		__entry->mode		= mode;
 	),
 
-- 
2.20.1