[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20190830160957.GC2634@redhat.com>
Date: Fri, 30 Aug 2019 18:09:57 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Russell King - ARM Linux admin <linux@...linux.org.uk>,
Peter Zijlstra <peterz@...radead.org>,
Chris Metcalf <cmetcalf@...hip.com>,
Christoph Lameter <cl@...ux.com>,
Kirill Tkhai <tkhai@...dex.ru>, Mike Galbraith <efault@....de>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Use of probe_kernel_address() in task_rcu_dereference()
without checking return value
On 08/30, Linus Torvalds wrote:
>
> Side note: that code had better not be performance-critical, because
> "probe_kernel_address()" is actually really really slow.
Yes, please see
[PATCH 2/3] introduce probe_slab_address()
https://lore.kernel.org/lkml/20141027195425.GC11736@redhat.com/
I sent 5 years ago ;) Do you think
/*
* Same as probe_kernel_address(), but @addr must be the valid pointer
* to a slab object, potentially freed/reused/unmapped.
*/
#ifdef CONFIG_DEBUG_PAGEALLOC
#define probe_slab_address(addr, retval) \
probe_kernel_address(addr, retval)
#else
#define probe_slab_address(addr, retval) \
({ \
(retval) = *(typeof(retval) *)(addr); \
0; \
})
#endif
can work?
Oleg.
Powered by blists - more mailing lists