linux-kernel - Re: [syzbot] [kernel?] BUG: unable to handle kernel NULL pointer dereference in __hrtimer_run

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Date: Tue, 04 Jun 2024 18:10:04 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Will Deacon <will@...nel.org>
Cc: syzbot <syzbot+558f67d44ad7f098a3de@...kaller.appspotmail.com>,
 anna-maria@...utronix.de, frederic@...nel.org,
 linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, Catalin
 Marinas <catalin.marinas@....com>
Subject: Re: [syzbot] [kernel?] BUG: unable to handle kernel NULL pointer
 dereference in __hrtimer_run_queues

Will!

On Tue, Jun 04 2024 at 14:34, Will Deacon wrote:
> On Tue, Jun 04, 2024 at 02:29:57PM +0200, Thomas Gleixner wrote:
>> On Mon, Jun 03 2024 at 03:22, syzbot wrote:
>> > * 10:	f9400821 	ldr	x1, [x1, #16] <-- trapping instruction
>> 		while (node->rb_left)
>> 
>> > x2 : ff7000007f8cf8e8 x1 : 0000000000000080 x0 : 0000000000000080
>> 
>> which obviously crashes. Now the question is how does the original node
>> end up with node::rb_right == 0x80?
>> 
>> I doubt that this is a hrtimer or rbtree problem. It smells like random
>> data corruption caused by whatever. It might not even be an ARM64
>> specific issue though the C repro does not trigger on x86...
>> 
>> Handing it over to Catalin and Will.
>
> I suspect this is a duplicate of:
>
> https://lore.kernel.org/lkml/20240604110119.GA20284@willie-the-truck/
>
> and there's a fix queued in the -mm tree.

That looks very much so.

Thanks,

        tglx