On 4/17/20 9:09 AM, Bernard Zhao wrote: > kmalloc size should never exceed KMALLOC_MAX_SIZE. > kmalloc_index realise if size is exceed KMALLOC_MAX_SIZE, e.g 64M, > kmalloc_index just return index 26, but never check with OS`s max > kmalloc config KMALLOC_MAX_SIZE. This index`s kmalloc caches maybe > not create in function create_kmalloc_caches. > We can throw an warninginfo in kmalloc at the beginning, instead of > being guaranteed by the buddy alloc behind. > > Signed-off-by: Bernard Zhao <bernard@xxxxxxxx> kmalloc_index() is only called from kmalloc() and kmalloc_node() for compile-time constant sizes up to KMALLOC_MAX_CACHE_SIZE, which is smaller (SLUB, SLOB) or equal (SLAB) than KMALLOC_MAX_SIZE. So your patch is effectively a no-op and we better shouldn't tease the compiler too much, so that kmalloc_index() stays fully compile-time evaluated. > --- > include/linux/slab.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 6d45488..59b60d2 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -351,6 +351,10 @@ static __always_inline unsigned int kmalloc_index(size_t size) > if (!size) > return 0; > > + /* size should never exceed KMALLOC_MAX_SIZE. */ > + if (size > KMALLOC_MAX_SIZE) > + WARN(1, "size exceed max kmalloc size!\n"); > + > if (size <= KMALLOC_MIN_SIZE) > return KMALLOC_SHIFT_LOW; > >
