[kbuild-all] [linux-next:master 10679/10701] arch/x86/mm/pgtable.c:427:2: warning: variable length array 'u_pmds' is used

tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master head: fb57b1fabcb28f358901b2df90abd2b48abc1ca8 commit: 0e19fc1c40bd7516d5a30a459db4f49d48910847 [10679/10701] mm: consolidate pgd_index() and pgd_offset{_k}() definitions config: i386-randconfig-a005-20200520 (attached as .config) compiler: gcc-4.9 (Ubuntu 4.9.3-13ubuntu2) 4.9.3 reproduce: git checkout 0e19fc1c40bd7516d5a30a459db4f49d48910847 # save the attached .config to linux build tree make ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kbuild test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>, old ones prefixed by <<): arch/x86/mm/pgtable.c: In function 'pgd_alloc': pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS]; ^ pmd_t *pmds[MAX_PREALLOCATED_PMDS]; ^ vim +/u_pmds +427 arch/x86/mm/pgtable.c 1db491f77b6ed0 Fenghua Yu 2015-01-15 423 d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 424 pgd_t *pgd_alloc(struct mm_struct *mm) 1ec1fe73dfb711 Ingo Molnar 2008-03-19 425 { d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 426 pgd_t *pgd; 184d47f0fd3651 Kees Cook 2018-10-08 @427 pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS]; 184d47f0fd3651 Kees Cook 2018-10-08 @428 pmd_t *pmds[MAX_PREALLOCATED_PMDS]; 1ec1fe73dfb711 Ingo Molnar 2008-03-19 429 1db491f77b6ed0 Fenghua Yu 2015-01-15 430 pgd = _pgd_alloc(); 1ec1fe73dfb711 Ingo Molnar 2008-03-19 431 d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 432 if (pgd == NULL) d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 433 goto out; 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 434 d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 435 mm->pgd = pgd; 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 436 f59dbe9ca6707e Joerg Roedel 2018-07-18 437 if (preallocate_pmds(mm, pmds, PREALLOCATED_PMDS) != 0) d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 438 goto out_free_pgd; d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 439 f59dbe9ca6707e Joerg Roedel 2018-07-18 440 if (preallocate_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS) != 0) d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 441 goto out_free_pmds; d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 442 f59dbe9ca6707e Joerg Roedel 2018-07-18 443 if (paravirt_pgd_alloc(mm) != 0) f59dbe9ca6707e Joerg Roedel 2018-07-18 444 goto out_free_user_pmds; f59dbe9ca6707e Joerg Roedel 2018-07-18 445 d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 446 /* d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 447 * Make sure that pre-populating the pmds is atomic with d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 448 * respect to anything walking the pgd_list, so that they d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 449 * never see a partially populated pgd. d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 450 */ a79e53d85683c6 Andrea Arcangeli 2011-02-16 451 spin_lock(&pgd_lock); 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 452 617d34d9e5d832 Jeremy Fitzhardinge 2010-09-21 453 pgd_ctor(mm, pgd); d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 454 pgd_prepopulate_pmd(mm, pgd, pmds); f59dbe9ca6707e Joerg Roedel 2018-07-18 455 pgd_prepopulate_user_pmd(mm, pgd, u_pmds); 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 456 a79e53d85683c6 Andrea Arcangeli 2011-02-16 457 spin_unlock(&pgd_lock); 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 458 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 459 return pgd; d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 460 f59dbe9ca6707e Joerg Roedel 2018-07-18 461 out_free_user_pmds: f59dbe9ca6707e Joerg Roedel 2018-07-18 462 free_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS); d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 463 out_free_pmds: f59dbe9ca6707e Joerg Roedel 2018-07-18 464 free_pmds(mm, pmds, PREALLOCATED_PMDS); d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 465 out_free_pgd: 1db491f77b6ed0 Fenghua Yu 2015-01-15 466 _pgd_free(pgd); d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 467 out: d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25 468 return NULL; 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 469 } 4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17 470 :::::: The code at line 427 was first introduced by commit :::::: 184d47f0fd365108bd06ab26cdb3450b716269fd x86/mm: Avoid VLA in pgd_alloc() :::::: TO: Kees Cook <keescook(a)chromium.org&gt; :::::: CC: Ingo Molnar <mingo(a)kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org