Messages in this thread | | | Date | Fri, 18 Apr 2014 13:09:35 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH 3/8] idr: fix NULL pointer dereference when ida_remove(unallocated_id) |
| |
On Fri, Apr 18, 2014 at 08:49:50PM +0800, Lai Jiangshan wrote: > If the ida has at least one existed_id, and when an special unallocated_id
existing id or allocated id
when an unallocated id which meets a certain condition is passed to...
> is passed to the ida_remove(), the system will crash because it hits NULL > pointer dereference. > > This special unallocated_id is that it shares the same lowest idr layer with
The condition is that the ID shares the...
> an exsited_id, but the idr slot is different(if the unallocated_id is allocated).
the existing ID, would be different if the unallocated ID were to be allocated.
> In this case the supposed idr slot of the unallocated_id is NULL,
matching for
> It means @bitmap == NULL, and when the code dereference it, it crash the kernel.
causing @bitmap to be NULL which the function dereferences without checking crashing the kernel.
> > See the test code: > > static void test3(void) > { > int id; > DEFINE_IDA(test_ida); > > printk(KERN_INFO "Start test3\n"); > if (ida_pre_get(&test_ida, GFP_KERNEL) < 0) return; > if (ida_get_new(&test_ida, &id) < 0) return; > ida_remove(&test_ida, 4000); /* bug: null deference here */ > printk(KERN_INFO "End of test3\n"); > } > > It only happens when unallocated_id, it is caller's fault. It is not
It happens only when the caller tries to free an unallocated ID which is the caller's fault.
> a bug. But it is better to add the proper check and complains instead
and complain rather than crashing the kernel
> of crashing the kernel. > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Tejun Heo <tj@kernel.org>
Thanks.
-- tejun
| |