linux-kernel - Re: [V2][PATCH] rcu: avoid alloc

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Message-ID: <20211116203405.GU641268@paulmck-ThinkPad-P17-Gen-1>
Date:   Tue, 16 Nov 2021 12:34:05 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     Jun Miao <jun.miao@...el.com>, urezki@...il.com, elver@...gle.com,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        joel@...lfernandes.org, qiang.zhang1211@...il.com,
        rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, jianwei.hu@...driver.com
Subject: Re: [V2][PATCH] rcu: avoid alloc_pages() when recording stack

On Tue, Nov 16, 2021 at 05:39:59PM +0000, Juri Lelli wrote:
> Hi,
> 
> On 16/11/21 07:23, Jun Miao wrote:
> > The default kasan_record_aux_stack() calls stack_depot_save() with GFP_NOWAIT,
> > which in turn can then call alloc_pages(GFP_NOWAIT, ...).  In general, however,
> > it is not even possible to use either GFP_ATOMIC nor GFP_NOWAIT in certain
> > non-preemptive contexts/RT kernel including raw_spin_locks (see gfp.h and ab00db216c9c7).
> > Fix it by instructing stackdepot to not expand stack storage via alloc_pages()
> > in case it runs out by using kasan_record_aux_stack_noalloc().
> > 
> > Jianwei Hu reported:
> > BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969
> > in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 15319, name: python3
> > INFO: lockdep is turned off.
> > irq event stamp: 0
> >   hardirqs last  enabled at (0): [<0000000000000000>] 0x0
> >   hardirqs last disabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
> >   softirqs last  enabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
> >   softirqs last disabled at (0): [<0000000000000000>] 0x0
> >   CPU: 6 PID: 15319 Comm: python3 Tainted: G        W  O 5.15-rc7-preempt-rt #1
> >   Hardware name: Supermicro SYS-E300-9A-8C/A2SDi-8C-HLN4F, BIOS 1.1b 12/17/2018
> >   Call Trace:
> >     show_stack+0x52/0x58
> >     dump_stack+0xa1/0xd6
> >     ___might_sleep.cold+0x11c/0x12d
> >     rt_spin_lock+0x3f/0xc0
> >     rmqueue+0x100/0x1460
> >     rmqueue+0x100/0x1460
> >     mark_usage+0x1a0/0x1a0
> >     ftrace_graph_ret_addr+0x2a/0xb0
> >     rmqueue_pcplist.constprop.0+0x6a0/0x6a0
> >      __kasan_check_read+0x11/0x20
> >      __zone_watermark_ok+0x114/0x270
> >      get_page_from_freelist+0x148/0x630
> >      is_module_text_address+0x32/0xa0
> >      __alloc_pages_nodemask+0x2f6/0x790
> >      __alloc_pages_slowpath.constprop.0+0x12d0/0x12d0
> >      create_prof_cpu_mask+0x30/0x30
> >      alloc_pages_current+0xb1/0x150
> >      stack_depot_save+0x39f/0x490
> >      kasan_save_stack+0x42/0x50
> >      kasan_save_stack+0x23/0x50
> >      kasan_record_aux_stack+0xa9/0xc0
> >      __call_rcu+0xff/0x9c0
> >      call_rcu+0xe/0x10
> >      put_object+0x53/0x70
> >      __delete_object+0x7b/0x90
> >      kmemleak_free+0x46/0x70
> >      slab_free_freelist_hook+0xb4/0x160
> >      kfree+0xe5/0x420
> >      kfree_const+0x17/0x30
> >      kobject_cleanup+0xaa/0x230
> >      kobject_put+0x76/0x90
> >      netdev_queue_update_kobjects+0x17d/0x1f0
> >      ... ...
> >      ksys_write+0xd9/0x180
> >      __x64_sys_write+0x42/0x50
> >      do_syscall_64+0x38/0x50
> >      entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> > Links: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/include/linux/kasan.h?id=7cb3007ce2da27ec02a1a3211941e7fe6875b642
> > Fixes: 84109ab58590 ("rcu: Record kvfree_call_rcu() call stack for KASAN")
> > Fixes: 26e760c9a7c8 ("rcu: kasan: record and print call_rcu() call stack")
> > Reported-by: Jianwei Hu <jianwei.hu@...driver.com>
> > Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> > Signed-off-by: Jun Miao <jun.miao@...el.com>
> > ---
> 
> I gave this a quick try on RT. No splats. Nice!
> 
> Tested-by: Juri Lelli <juri.lelli@...hat.com>

Applied with Juri's Tested-by and Marco's Acked-by.  Thank you all!

							Thanx, Paul