Commit 7c61c35b authored Apr 29, 2022 by Miaohe Lin Committed by Andrew Morton May 27, 2022

mm/z3fold: fix possible null pointer dereferencing

alloc_slots could fail to allocate memory under heavy memory pressure.  So
we should check zhdr->slots against NULL to avoid future null pointer
dereferencing.

Link: https://lkml.kernel.org/r/20220429064051.61552-3-linmiaohe@huawei.com


Fixes: fc548865 ("z3fold: simplify freeing slots")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 4c6bdb36

mm/z3fold.c

+11 −1

Original line number	Original line	Diff line number	Diff line
	@@ -940,9 +940,19 @@ static inline struct z3fold_header __z3fold_alloc(struct z3fold_pool pool,
	}		}
	}		}

	if (zhdr && !zhdr->slots)		if (zhdr && !zhdr->slots) {
	zhdr->slots = alloc_slots(pool, GFP_ATOMIC);		zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
			if (!zhdr->slots)
			goto out_fail;
			}
	return zhdr;		return zhdr;

			out_fail:
			if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
			add_to_unbuddied(pool, zhdr);
			z3fold_page_unlock(zhdr);
			}
			return NULL;
	}		}

	/*		/*