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authorWaiman Long <longman@redhat.com>2022-04-08 13:09:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-04-08 14:20:36 -1000
commita431dbbc540532b7465eae4fc8b56a85a9fc7d17 (patch)
treeae5aee88b8eb18fa01fa3a76b33728b373db2c9a /include
parenteafc0a02391b7b36617b36c97c4b5d6832cf5e24 (diff)
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/mmzone.h11
1 files changed, 7 insertions, 4 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 962b14d403e8..46ffab808f03 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1397,13 +1397,16 @@ static inline unsigned long *section_to_usemap(struct mem_section *ms)
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);