On Fri, 1 Jun 2007, Linus Torvalds wrote: > So when I suggested the uglier > > if ((unsigned long)x <= 16) > return; > > I really did mean to use that ugly cast.. Yours is prettier, but sadly, > yours is simply not safe: a signed comparison might end up making _all_ > kernel pointers trigger that test.
Maybe we can have a compromise? Lets at least keep the ZERO_SIZE_PTR reference in there. SLUB: Make sure that the comparision with ZERO_SIZE_PTR is unsigned Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]> --- mm/slub.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) Index: slub/mm/slub.c =================================================================== --- slub.orig/mm/slub.c 2007-06-01 20:00:56.000000000 -0700 +++ slub/mm/slub.c 2007-06-01 20:04:26.000000000 -0700 @@ -2338,7 +2338,13 @@ void kfree(const void *x) struct kmem_cache *s; struct page *page; - if (x <= ZERO_SIZE_PTR) + /* + * This has to be an unsigned comparison. According to Linus + * some gcc version tread a pointer as a signed entity. Then + * this comparison would be true for all "negative" pointers + * (which would cover the whole upper half of the address space). + */ + if ((unsigned long)x <= (unsigned long)ZERO_SIZE_PTR) return; page = virt_to_head_page(x); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/