linux-kernel - Re: [PATCH v2] kasan: Don't call find_vm

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Message-ID: <d0d2c78d-9ea6-43c6-8413-97d21ff77bdd@gmail.com>
Date: Wed, 12 Feb 2025 18:54:02 +0100
From: Andrey Ryabinin <ryabinin.a.a@...il.com>
To: Waiman Long <longman@...hat.com>, Alexander Potapenko
 <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>,
 Dmitry Vyukov <dvyukov@...gle.com>,
 Vincenzo Frascino <vincenzo.frascino@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Clark Williams <clrkwllms@...nel.org>, Steven Rostedt <rostedt@...dmis.org>
Cc: kasan-dev@...glegroups.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
 Nico Pache <npache@...hat.com>
Subject: Re: [PATCH v2] kasan: Don't call find_vm_area() in RT kernel



On 2/12/25 5:21 PM, Waiman Long 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
> 
> Commit e30a0361b851 ("kasan: make report_lock a raw spinlock")
> changes report_lock to a raw_spinlock_t to avoid a similar RT problem.
> The print_address_description() function is called with report_lock
> acquired and interrupt disabled.  However, the find_vm_area() function
> still 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 and
> changing report_lock to a raw_spinlock_t is not enough to completely
> solve this RT kernel problem.
> 
> 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.
> 
> Fixes: e30a0361b851 ("kasan: make report_lock a raw spinlock")
> Signed-off-by: Waiman Long <longman@...hat.com>
> ---
>  mm/kasan/report.c | 47 ++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 34 insertions(+), 13 deletions(-)
> 
>  [v2] Encapsulate the change into a new
>       kasan_print_vmalloc_info_ret_page() helper
> 

Not exactly what I had i mind, but this way is fine too.

Acked-by: Andrey Ryabinin <ryabinin.a.a@...il.com>