Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH] x86: avoid VLA in pgd_alloc() | Date | Fri, 5 Oct 2018 18:13:16 +0200 |
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Turning on -Wvla found a new VLA usage:
In file included from include/linux/kernel.h:15, from include/asm-generic/bug.h:18, from arch/x86/include/asm/bug.h:83, from include/linux/bug.h:5, from include/linux/mmdebug.h:5, from include/linux/mm.h:9, from arch/x86/mm/pgtable.c:2: arch/x86/mm/pgtable.c: In function 'pgd_alloc': include/linux/build_bug.h:29:45: error: ISO C90 forbids variable length array 'u_pmds' [-Werror=vla] arch/x86/mm/pgtable.c:190:34: note: in expansion of macro 'static_cpu_has' #define PREALLOCATED_USER_PMDS (static_cpu_has(X86_FEATURE_PTI) ? \ ^~~~~~~~~~~~~~ arch/x86/mm/pgtable.c:431:16: note: in expansion of macro 'PREALLOCATED_USER_PMDS' pmd_t *u_pmds[PREALLOCATED_USER_PMDS]; ^~~~~~~~~~~~~~~~~~~~~~
Use the actual size of the array that is used for X86_FEATURE_PTI instead of the variable size.
Fixes: f59dbe9ca670 ("x86/pgtable/pae: Use separate kernel PMDs for user page-table") Fixes: 68664695ae57 ("Makefile: Globally enable VLA warning") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/x86/mm/pgtable.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 089e78c4effd..386b43e3e0ac 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -189,6 +189,7 @@ static void pgd_dtor(pgd_t *pgd) */ #define PREALLOCATED_USER_PMDS (static_cpu_has(X86_FEATURE_PTI) ? \ KERNEL_PGD_PTRS : 0) +#define MAX_PREALLOCATED_USER_PMDS KERNEL_PGD_PTRS void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd) { @@ -211,6 +212,7 @@ void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd) /* No need to prepopulate any pagetable entries in non-PAE modes. */ #define PREALLOCATED_PMDS 0 #define PREALLOCATED_USER_PMDS 0 +#define MAX_PREALLOCATED_USER_PMDS 0 #endif /* CONFIG_X86_PAE */ static void free_pmds(struct mm_struct *mm, pmd_t *pmds[], int count) @@ -428,8 +430,8 @@ static inline void _pgd_free(pgd_t *pgd) pgd_t *pgd_alloc(struct mm_struct *mm) { pgd_t *pgd; - pmd_t *u_pmds[PREALLOCATED_USER_PMDS]; - pmd_t *pmds[PREALLOCATED_PMDS]; + pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS]; + pmd_t *pmds[MAX_PREALLOCATED_USER_PMDS]; pgd = _pgd_alloc(); -- 2.18.0
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