Messages in this thread | | | Subject | Re: [PATCH]highmem_32.c: add argument pointer checking | From | "Figo.zhang" <> | Date | Tue, 30 Jun 2009 00:11:03 +0800 |
| |
On Mon, 2009-06-29 at 06:09 +0200, Ingo Molnar wrote: > * Figo.zhang <figo1802@gmail.com> wrote: > > > It had better add argument pointer checking. > > > > If any guys write driver want to alloc hightmem and pass a no-initial pointer, > > it would be crashed. > > > > Signed-off-by: Figo.zhang <figo1802@gmail.com> > > --- > > arch/x86/mm/highmem_32.c | 4 ++++ > > 1 files changed, 4 insertions(+), 0 deletions(-) > > > > diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c > > index 58f621e..e52e1a9 100644 > > --- a/arch/x86/mm/highmem_32.c > > +++ b/arch/x86/mm/highmem_32.c > > @@ -31,6 +31,7 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot) > > { > > enum fixed_addresses idx; > > unsigned long vaddr; > > + BUG_ON(!page); > > > > /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */ > > pagefault_disable(); > > @@ -58,6 +59,9 @@ void kunmap_atomic(void *kvaddr, enum km_type type) > > unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK; > > enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id(); > > > > + if(!kvaddr) > > + return; > > + > > (Please run patches through scripts/checkpatch.pl before > submission.) > > Also, what's the improvement here? Before the patch we'd crash on a > NULL dereference ... after the patch we'd crash on a BUG_ON().
why it would be crash on BUG_ON()? I motify it and test on my computer, it would not crash.
Best Regards, Figo.zhang
> > Furthermore, he kunmap_atomic() change is outright wrong - it will > now allow NULL kunmaps, which can hide bugs in drivers. > > Ingo
| |