Messages in this thread | | | Date | Mon, 29 Jun 2009 06:09:54 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH]highmem_32.c: add argument pointer checking |
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* 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().
Furthermore, he kunmap_atomic() change is outright wrong - it will now allow NULL kunmaps, which can hide bugs in drivers.
Ingo
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