linux-kernel - [PATCH] mm/large system hash: avoid possible NULL deref in alloc_large_system

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Message-Id: <20210915212530.2321545-1-eric.dumazet@gmail.com>
Date:   Wed, 15 Sep 2021 14:25:30 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Nicholas Piggin <npiggin@...il.com>
Subject: [PATCH] mm/large system hash: avoid possible NULL deref in alloc_large_system_hash

From: Eric Dumazet <edumazet@...gle.com>

If __vmalloc() returned NULL, is_vm_area_hugepages(NULL) will fault
if CONFIG_HAVE_ARCH_HUGE_VMALLOC=y

Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Nicholas Piggin <npiggin@...il.com>
---
 mm/page_alloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b37435c274cf1cb1fabd26465ca7899bb610d91f..e115e21524739341d409b28379942241ed403060 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8756,7 +8756,8 @@ void *__init alloc_large_system_hash(const char *tablename,
 		} else if (get_order(size) >= MAX_ORDER || hashdist) {
 			table = __vmalloc(size, gfp_flags);
 			virt = true;
-			huge = is_vm_area_hugepages(table);
+			if (table)
+				huge = is_vm_area_hugepages(table);
 		} else {
 			/*
 			 * If bucketsize is not a power-of-two, we may free
-- 
2.33.0.309.g3052b89438-goog