lkml.org 
[lkml]   [2009]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH]highmem_32.c: add argument pointer checking

* 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


\
 
 \ /
  Last update: 2009-06-29 06:13    [W:0.028 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site