netdev - Re: [GIT PULL] Networking for v6.9

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Message-ID: <fee2fccf-ef4d-4595-8f20-07ba4dc67d42@kernel.dk>
Date: Tue, 12 Mar 2024 16:02:08 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
 Johannes Thumshirn <johannes.thumshirn@....com>, davem@...emloft.net,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, pabeni@...hat.com,
 bpf@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: Re: [GIT PULL] Networking for v6.9

On 3/12/24 3:55 PM, Jakub Kicinski wrote:
> On Tue, 12 Mar 2024 14:48:06 -0700 Jakub Kicinski wrote:
>>> index 9a85bfbbc45a..646b50e1c914 100644
>>> --- a/block/blk-iocost.c
>>> +++ b/block/blk-iocost.c
>>> @@ -1044,7 +1044,7 @@ static void ioc_now(struct ioc *ioc, struct ioc_now *now)
>>>  	unsigned seq;
>>>  	u64 vrate;
>>>  
>>> -	now->now_ns = blk_time_get_ns();
>>> +	now->now_ns = ktime_get_ns();
>>>  	now->now = ktime_to_us(now->now_ns);
>>>  	vrate = atomic64_read(&ioc->vtime_rate);  
>>
>> Let me try this, 'cause doing the revert while listening to some
>> meeting is beyond me :)
> 
> That fixes the crash for me!

OK good, thanks for testing! Linus, can you just pick up the below? I
can prep a pull as well, but not ready to send the remaining merge
window fixes just yet.

>From fb280ede759d1918fec03bc22d32eeaaa45500bb Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@...nel.dk>
Date: Tue, 12 Mar 2024 15:58:41 -0600
Subject: [PATCH] block: limit block time caching to in_task() context

We should not have any callers of this from non-task context, but Jakub
ran [1] into one from blk-iocost. Rather than risk running into others,
or future ones, just limit blk_time_get_ns() to when it is called from
a task. Any other usage is invalid.

[1] https://lore.kernel.org/lkml/CAHk-=wiOaBLqarS2uFhM1YdwOvCX4CZaWkeyNDY1zONpbYw2ig@mail.gmail.com/

Fixes: da4c8c3d0975 ("block: cache current nsec time in struct blk_plug")
Reported-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
---
 block/blk.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk.h b/block/blk.h
index a19b7b42e650..5cac4e29ae17 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -534,7 +534,7 @@ static inline u64 blk_time_get_ns(void)
 {
 	struct blk_plug *plug = current->plug;
 
-	if (!plug)
+	if (!plug || !in_task())
 		return ktime_get_ns();
 
 	/*
-- 
2.43.0

-- 
Jens Axboe