On 2018/6/21 11:38, Matthew Wilcox wrote:
On Thu, Jun 21, 2018 at 11:07:14AM +0800, Jia-Ju Bai wrote:
The kernel may sleep with holding a spinlock.
The function call path (from bottom to top) in Linux-4.16.7 is:
[FUNC] remove_element(GFP_KERNEL)
mm/mempool.c, 250: remove_element in mempool_resize
mm/mempool.c, 247: _raw_spin_lock_irqsave in mempool_resize
To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
This bug is found by my static analysis tool (DSAC-2) and checked by
my code review.
But ... we don't use the flags argument.
static void *remove_element(mempool_t *pool, gfp_t flags)
{
void *element = pool->elements[--pool->curr_nr];
BUG_ON(pool->curr_nr < 0);
kasan_unpoison_element(pool, element, flags);
check_element(pool, element);
return element;
}
...
static void kasan_unpoison_element(mempool_t *pool, void *element, gfp_t flags)
{
if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
kasan_unpoison_slab(element);
if (pool->alloc == mempool_alloc_pages)
kasan_alloc_pages(element, (unsigned long)pool->pool_data);
}
So the correct patch would just remove this argument to remove_element() and
kasan_unpoison_element()?
Yes, I also find this.
I can submit a patch that removes the flag in:
Definitions of kasan_unpoison_element() and remove_element()
Three calls to remove_element() and one call to kasan_unpoison_element()
in mempool.c.
Do you think it is okay?
Best wishes,
Jia-Ju Bai
