| Message ID | 20200620033007.1444705-17-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Johannes Berg |
| Headers | show |
| Series | Remove uninitialized_var() macro | expand |
On Fri, Jun 19, 2020 at 8:30 PM Kees Cook <keescook@chromium.org> wrote: > > Using uninitialized_var() is dangerous as it papers over real bugs[1] > (or can in the future), and suppresses unrelated compiler warnings (e.g. > "unused variable"). If the compiler thinks it is uninitialized, either > simply initialize the variable or make compiler changes. As a precursor > to removing[2] this[3] macro[4], just initialize this variable to NULL. > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ > > Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers") > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > mm/debug_vm_pgtable.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index e45623016aea..83c9e88a052a 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -307,7 +307,7 @@ static int __init debug_vm_pgtable(void) > phys_addr_t paddr; > unsigned long vaddr, pte_aligned, pmd_aligned; > unsigned long pud_aligned, p4d_aligned, pgd_aligned; > - spinlock_t *uninitialized_var(ptl); > + spinlock_t *ptl = NULL; It looks like the address of ptl is passed to pte_alloc_map_lock. It looks like pte_offset_map_lock unconditionally assigns through that pointer before reading. So this could be left uninitialized, but initializing it doesn't hurt. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > pr_info("Validating architecture page table helpers\n"); > prot = vm_get_page_prot(VMFLAGS); > --
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index e45623016aea..83c9e88a052a 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -307,7 +307,7 @@ static int __init debug_vm_pgtable(void) phys_addr_t paddr; unsigned long vaddr, pte_aligned, pmd_aligned; unsigned long pud_aligned, p4d_aligned, pgd_aligned; - spinlock_t *uninitialized_var(ptl); + spinlock_t *ptl = NULL; pr_info("Validating architecture page table helpers\n"); prot = vm_get_page_prot(VMFLAGS);
Using uninitialized_var() is dangerous as it papers over real bugs[1] (or can in the future), and suppresses unrelated compiler warnings (e.g. "unused variable"). If the compiler thinks it is uninitialized, either simply initialize the variable or make compiler changes. As a precursor to removing[2] this[3] macro[4], just initialize this variable to NULL. [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ Fixes: 399145f9eb6c ("mm/debug: add tests validating architecture page table helpers") Signed-off-by: Kees Cook <keescook@chromium.org> --- mm/debug_vm_pgtable.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)