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Date: Tue, 11 Feb 2025 14:57:30 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Waiman Long <longman@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>, Alexander Potapenko
 <glider@google.com>, Andrey Konovalov <andreyknvl@gmail.com>, Dmitry Vyukov
 <dvyukov@google.com>, Vincenzo Frascino <vincenzo.frascino@arm.com>,
 Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Clark Williams
 <clrkwllms@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
 kasan-dev@googlegroups.com, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Nico Pache
 <npache@redhat.com>
Subject: Re: [PATCH] kasan: Don't call find_vm_area() in RT kernel
Message-Id: <20250211145730.5ff45281943b5b044208372c@linux-foundation.org>
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On Tue, 11 Feb 2025 11:07:50 -0500 Waiman Long <longman@redhat.com> wrote:

> The following bug report appeared with a test run in a RT debug kernel.
> 
> [ 3359.353842] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> [ 3359.353848] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 140605, name: kunit_try_catch
> [ 3359.353853] preempt_count: 1, expected: 0
>   :
> [ 3359.353933] Call trace:
>   :
> [ 3359.353955]  rt_spin_lock+0x70/0x140
> [ 3359.353959]  find_vmap_area+0x84/0x168
> [ 3359.353963]  find_vm_area+0x1c/0x50
> [ 3359.353966]  print_address_description.constprop.0+0x2a0/0x320
> [ 3359.353972]  print_report+0x108/0x1f8
> [ 3359.353976]  kasan_report+0x90/0xc8
> [ 3359.353980]  __asan_load1+0x60/0x70
> 
> The print_address_description() is run with a raw_spinlock_t acquired
> and interrupt disabled. The find_vm_area() function needs to acquire
> a spinlock_t which becomes a sleeping lock in the RT kernel. IOW,
> we can't call find_vm_area() in a RT kernel. Fix this bug report
> by skipping the find_vm_area() call in this case and just print out
> the address as is.
> 
> For !RT kernel, follow the example set in commit 0cce06ba859a
> ("debugobjects,locking: Annotate debug_object_fill_pool() wait type
> violation") and use DEFINE_WAIT_OVERRIDE_MAP() to avoid a spinlock_t
> inside raw_spinlock_t warning.
> 

Thanks.  I added it and shall await review from the KASAN developers.

I'm thinking we add

Fixes: c056a364e954 ("kasan: print virtual mapping info in reports")
Cc: <stable@vger.kernel.org>

but c056a364e954 is 3 years old and I don't think we care about -rt in
such old kernels.  Thoughts?