Messages in this thread | | | Date | Fri, 9 Jul 2021 09:57:45 +0300 | From | Pavel Skripkin <> | Subject | Re: BUG in alloc_workqueue (linux-next) |
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On Fri, 9 Jul 2021 11:59:01 +0800 Lai Jiangshan <jiangshanlai@gmail.com> wrote:
> Hello, Pavel > Thanks for the report. > > Huawei (CC-ed) is also dealing with the problem: > https://lore.kernel.org/lkml/20210708093136.2195752-1-yangyingliang@huawei.com/t/#u > > > Could you have a try on the fix, please? > > Thanks > Lai >
Hi, Lai!
I am going to apply this patch to my local tree and let syzbot test the fix for a day. Will reply to this email with results tomorrow :)
With regards, Pavel Skripkin
> On Thu, Jul 8, 2021 at 9:24 PM Pavel Skripkin <paskripkin@gmail.com> > wrote: > > > > > I've spent some time trying to came up with a fix, but I gave > > up :( But! I have an idea about what's happening, maybe it will help > > somehow... > > > > > > So, all 3 reports have same stack trace: alloc_workqueue() in > > loop_configure(). I skimmed through syzbot's log and found, that > > syzbot injected failure into alloc_unbound_pwq() in all 3 cases: > > > > FAULT_INJECTION: forcing a failure. > > name failslab, interval 1, probability 0, space 0, times 0 > > CPU: 1 PID: 17986 Comm: syz-executor.0 Tainted: G W > > 5.13.0-next-20210706 #9 Hardware name: QEMU Standard PC (i440FX + > > PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org > > 04/01/2014 Call Trace: dump_stack_lvl (lib/dump_stack.c:106 > > (discriminator 4)) should_fail.cold (lib/fault-inject.c:52 > > lib/fault-inject.c:146) should_failslab (mm/slab_common.c:1327) > > kmem_cache_alloc_node (mm/slab.h:487 mm/slub.c:2902 > > mm/slub.c:3017) ? alloc_unbound_pwq (kernel/workqueue.c:3813) > > alloc_unbound_pwq (kernel/workqueue.c:3813) > > apply_wqattrs_prepare (kernel/workqueue.c:3963) > > apply_workqueue_attrs_locked (kernel/workqueue.c:4041) > > alloc_workqueue (kernel/workqueue.c:4078 kernel/workqueue.c:4201 > > kernel/workqueue.c:4309) > > > > > > So, if alloc_unbound_pwq() fails, apply_wqattrs_prepare() will jump > > to this code: > > > > out_free: > > free_workqueue_attrs(tmp_attrs); > > free_workqueue_attrs(new_attrs); > > apply_wqattrs_cleanup(ctx); <----| > > return NULL; | > > | > > put_pwq_unlocked() -> put_pwq() -> > > schedule_work(&pwq->unbound_release_work); > > > > > > and apply_wqattrs_cleanup() will schedule > > pwq_unbound_release_workfn() [2], but alloc_workqueue() will free > > workqueue_struct in case of alloc_unbound_pwq() error [1]. In that > > case we will get UAF in pwq_unbound_release_workfn() like in 3rd > > report. > > > > > > Does written above make some sence? :) > > > > > > > > With regards, > > Pavel Skripkin
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