From: Andrew Morton <akpm@linux-foundation.org>
To: mingo@kernel.org, kirill.shutemov@linux.intel.com,
jforbes@redhat.com, aquini@redhat.com, longman@redhat.com,
akpm@linux-foundation.org, patches@lists.linux.dev,
linux-mm@kvack.org, mm-commits@vger.kernel.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org
Subject: [patch 4/9] mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
Date: Fri, 08 Apr 2022 13:09:01 -0700 [thread overview]
Message-ID: <20220408200902.A24A9C385A1@smtp.kernel.org> (raw)
In-Reply-To: <20220408130819.a89195e527ce58dfbe0700b9@linux-foundation.org>
From: Waiman Long <longman@redhat.com>
Subject: mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning
The gcc 12 compiler reports a "'mem_section' will never be NULL" warning
on the following code:
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
#ifdef CONFIG_SPARSEMEM_EXTREME
if (!mem_section)
return NULL;
#endif
if (!mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
:
It happens with CONFIG_SPARSEMEM_EXTREME off. The mem_section definition
is
#ifdef CONFIG_SPARSEMEM_EXTREME
extern struct mem_section **mem_section;
#else
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
#endif
In the !CONFIG_SPARSEMEM_EXTREME case, mem_section
is a static 2-dimensional array and so the check
"!mem_section[SECTION_NR_TO_ROOT(nr)]" doesn't make sense.
Fix this warning by moving the "!mem_section[SECTION_NR_TO_ROOT(nr)]"
check up inside the CONFIG_SPARSEMEM_EXTREME block and adding an explicit
NR_SECTION_ROOTS check to make sure that there is no out-of-bound array
access.
Link: https://lkml.kernel.org/r/20220331180246.2746210-1-longman@redhat.com
Fixes: 3e347261a80b ("sparsemem extreme implementation")
Signed-off-by: Waiman Long <longman@redhat.com>
Reported-by: Justin Forbes <jforbes@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/mmzone.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/include/linux/mmzone.h~mm-sparsemem-fix-mem_section-will-never-be-null-gcc-12-warning
+++ a/include/linux/mmzone.h
@@ -1397,13 +1397,16 @@ static inline unsigned long *section_to_
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
+ unsigned long root = SECTION_NR_TO_ROOT(nr);
+
+ if (unlikely(root >= NR_SECTION_ROOTS))
+ return NULL;
+
#ifdef CONFIG_SPARSEMEM_EXTREME
- if (!mem_section)
+ if (!mem_section || !mem_section[root])
return NULL;
#endif
- if (!mem_section[SECTION_NR_TO_ROOT(nr)])
- return NULL;
- return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
+ return &mem_section[root][nr & SECTION_ROOT_MASK];
}
extern size_t mem_section_usage_size(void);
_
next prev parent reply other threads:[~2022-04-08 20:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 20:08 incoming Andrew Morton
2022-04-08 20:08 ` [patch 1/9] mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation Andrew Morton
2022-04-08 20:10 ` Matthew Wilcox
2022-04-08 20:08 ` [patch 2/9] highmem: fix checks in __kmap_local_sched_{in,out} Andrew Morton
2022-04-08 20:08 ` [patch 3/9] lz4: fix LZ4_decompress_safe_partial read out of bound Andrew Morton
2022-04-08 20:09 ` Andrew Morton [this message]
2022-04-11 9:00 ` [patch 4/9] mm/sparsemem: fix 'mem_section' will never be NULL gcc 12 warning Oscar Salvador
2022-04-08 20:09 ` [patch 5/9] mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) Andrew Morton
2022-04-08 20:09 ` [patch 6/9] mm/mempolicy: fix mpol_new leak in shared_policy_replace Andrew Morton
2022-04-08 20:09 ` [patch 7/9] mailmap: update Vasily Averin's email address Andrew Morton
2022-04-08 20:09 ` [patch 8/9] mm/list_lru.c: revert "mm/list_lru: optimize memcg_reparent_list_lru_node()" Andrew Morton
2022-04-08 20:09 ` [patch 9/9] MAINTAINERS: add Tom as clang reviewer Andrew Morton
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