From: Waiman Long <longman@redhat.com> stable inclusion from stable-v5.10.111 commit 5c672073bcca537a0880257f31c6d942388df046 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5GL1Z Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit a431dbbc540532b7465eae4fc8b56a85a9fc7d17 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Reviewed-by: Wei Li <liwei391@huawei.com> --- include/linux/mmzone.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 7e1e09fe4e3b..13c7a048e5ab 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1282,13 +1282,16 @@ 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 unsigned long __section_nr(struct mem_section *ms); extern size_t mem_section_usage_size(void); -- 2.20.1