Re: [PATCH] rcu: avoid alloc_pages() when recording stack

[Jun Miao]

Add KASAN maintainers

On 11/1/21 6:31 PM, 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
>
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Jun Miao <jun.miao@xxxxxxxxxxxxx>
> ---
>   kernel/rcu/tree.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8270e58cd0f3..2c1034580f15 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3026,7 +3026,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
>   	head->func = func;
>   	head->next = NULL;
>   	local_irq_save(flags);
> -	kasan_record_aux_stack(head);
> +	kasan_record_aux_stack_noalloc(head);
>   	rdp = this_cpu_ptr(&rcu_data);
>   
>   	/* Add the callback to our list. */
> @@ -3591,7 +3591,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
>   		return;
>   	}
>   
> -	kasan_record_aux_stack(ptr);
> +	kasan_record_aux_stack_noalloc(ptr);
>   	success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
>   	if (!success) {
>   		run_page_cache_worker(krcp);