In the Linux kernel, the following vulnerability has been resolved:

quota: Fix potential NULL pointer dereference

Below race may cause NULL pointer dereference

P1					P2
dquot_free_inode			quota_off
					  drop_dquot_ref
					   remove_dquot_ref
					   dquots = i_dquot(inode)
  dquots = i_dquot(inode)
  srcu_read_lock
  dquots[cnt]) != NULL (1)
					     dquots[type] = NULL (2)
  spin_lock(&dquots[cnt]->dq_dqb_lock) (3)
   ....

If dquot_free_inode(or other routines) checks inode's quota pointers (1)
before quota_off sets it to NULL(2) and use it (3) after that, NULL pointer
dereference will be triggered.

So let's fix it by using a temporary pointer to avoid this issue.

kernel.org https://git.kernel.org/stable/c/1ca72a3de915f87232c9a4cb9bebbd3af8ed3e25 [No types assigned]

kernel.org https://git.kernel.org/stable/c/40a673b4b07efd6f74ff3ab60f38b26aa91ee5d5 [No types assigned]

kernel.org https://git.kernel.org/stable/c/49669f8e7eb053f91d239df7b1bfb4500255a9d0 [No types assigned]

kernel.org https://git.kernel.org/stable/c/61380537aa6dd32d8a723d98b8f1bd1b11d8fee0 [No types assigned]

kernel.org https://git.kernel.org/stable/c/6afc9f4434fa8063aa768c2bf5bf98583aee0877 [No types assigned]

kernel.org https://git.kernel.org/stable/c/7f9e833fc0f9b47be503af012eb5903086939754 [No types assigned]

kernel.org https://git.kernel.org/stable/c/8514899c1a4edf802f03c408db901063aa3f05a1 [No types assigned]

kernel.org https://git.kernel.org/stable/c/d0aa72604fbd80c8aabb46eda00535ed35570f1f [No types assigned]

kernel.org https://git.kernel.org/stable/c/f2649d98aa9ca8623149b3cb8df00c944f5655c7 [No types assigned]