hugetlb: fix NULL pointer dereference in trace_hugetlbfs_alloc_inode

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.

Link: https://lkml.kernel.org/r/20250106033118.4640-1-songmuchun@bytedance.com
Fixes: 318580ad7f28 ("hugetlbfs: support tracepoint")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reported-by: Cheung Wall <zzqq0103.hey@gmail.com>
Closes: https://lore.kernel.org/linux-mm/02858D60-43C1-4863-A84F-3C76A8AF1F15@linux.dev/T/#
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Cc: cheung wall <zzqq0103.hey@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/trace/events/hugetlbfs.h b/include/trace/events/hugetlbfs.h
index 8331c904a9ba871ecc159925c4ddea38dc0fa2d4..59605dfaeeb43d9e7657e338fdbe740e8486a286 100644 (file)
--- 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;
        ),